Hole punch element

A hole punch device that reduces the force required to create a hole in papers or other sheet media. A punch element of the hole punch device includes a locally sloped or indented floor to create a bend in the sheet media as it is punched to create an enlarged, oval hole. The punch pin may include an expanding sleeve surround the pin that forms a larger diameter during the cutting stroke and springs back to a smaller diameter during a pull out stroke. A coiled torsion return spring is positioned remotely from and non-coaxially with the punch pin. A keyed pin and support frame arrangement ensures a predetermined rotational orientation of the pin for sequential cutting for reduced cutting force. A long lead-in surface in the frame helps installing sheet media into the feed slot of the punch element.

FIELD OF THE INVENTION

The present invention relates to hole punching devices used to cut holes in sheet material. More precisely, the present invention relates to a punch pin and support structure.

BACKGROUND OF THE INVENTION

A paper punch is a common device found in offices and schools. It is used to cut holes in paper under finger or hand pressure. Typically, a paper punch element includes a pin, and a frame to support the pin over a paper slot. The pin moves axially, or vertically, into the papers. It is desirable to minimize the force required to cut a hole into a stack of papers since these tools are usually operated under hand or finger pressure. To be sure, even a motorized paper punching device benefits from reduced force since a smaller motor may be used.

One method to reduce this force is to cut progressively around the perimeter of a hole rather than to cut the entire perimeter of the hole all at once. A well-known method for making a progressive cut is with a “V” cut notch in the end face of the pin. This creates more than one cutting point. The notched end cuts from two opposed sides of the hole toward the center of the hole. The notched end provides two equal pointed ends of the pin that press the paper stack simultaneously. Other designs use asymmetrical points or three or more cutting points.

Another concern is jamming of the pin in the paper. Typically, as the pin advances into the hole, the inside diameter edge of the paper is stretched and dragged down into the hole along with the pin. Then as the pin is withdrawn out of the hole, the edges tend to flip upward and press hard around the pin in a cam action. The hole effectively acts as a one-way cleat, with the hole inner diameter serving as a diaphragm to hold the pin in the hole. The hole diameter cut in the paper is in fact smaller than the diameter of the pin.

The prior art paper hole punches typically contemplate a compression type die spring strong enough to overcome the highest anticipated pull out or retraction force. The pin can typically be retracted only by the spring. Therefore, the spring must provide that function under all circumstances. U.S. Pat. No. 4,757,733 (Barlow) shows a typical arrangement inFIG. 6. Ridge40transmits pressure to cap47atop each pin (cutting tool15). Helical spring45surrounds the pin. When the pin does not retract in this type of design, the paper becomes jammed in the punching device since there is no further way to force the pin out. This situation is familiar to most users of paper punches. Also, the force needed to compress the die spring directly adds to the hand or operating force required to cut the hole. When a small stack of papers is being cut, the spring force is often greater than the actual cutting force.

There are many hole punch tool and pin designs. For example, U.S. Pat. No. 5,730,038 (Evans et al.) shows a punch pin cutting end with specified groove depth in relation to a paper stack height, and a force sequence profile. U.S. Pat. No. 5,243,887 (Bonge, Jr.) shows a rectangular punch18fitted in the rectangular guide hole of a frame. The punch is pivotably attached to a lever and secured axially by pin24. U.S. Pat. No. 4,763,552 (Wagner) discloses a punch pin with a symmetric angled cutting end. U.S. Pat. No. 4,713,995 (Davi) shows a conventional punch element design, including a helical return spring around the pin, and a lever that can only press, not pull, the pin. U.S. Pat. No. 4,449,436 (Semerjian, et al.) shows a cylindrical punch pin that includes a slotted top. A lever rib normally engages the top of the punch pin. An inoperative position for the sheet punch is achieved by rotating the punch pin so that the slot aligns with the lever rib. The rib then moves into the slot rather than pressing the top of the pin. No apparent mechanism is disclosed to keep the punch pin in its operative rotational position. The Semerjian '436 patent furthers shows an asymmetrical pin with one cutting point longer than another.

U.S. Pat. No. 4,257,300 (Muzik) discloses a cylindrical punch pin where the pin is secured axially at an annular groove. A key fitted in a radial slot of the pin positions the pin rotationally. U.S. Pat. No. 3,721,144 (Yamamori) shows a tubular punch die element with thin walls and a sharpened lower end. U.S. Pat. No. 3,320,843 (Schott, Jr.) shows a tubular punch element that is ground sharp at its cutting end. U.S. Pat. No. 4,594,927 (Mori) shows a punch pin held axially in two ways. In one embodiment, a rod10passes through a drilled hole in the upper body of the punch pin. Alternatively, an annular groove fits in a slot of a pressing plate. With the annular groove, the punch pin is not rotationally fixed in position. The Mori '927 patent shows an inclined base where the pins cut holes in a progressing sequence. The angle is very slight, just adequate to create the sequential cuts while maintaining a reasonable height to the punch device. U.S. Pat. No. 4,656,907 (Hymmem) shows a paper punch that may be disassembled for, among other reasons, to fix jammed pins. U.S. Pat. No. 4,240,572 (Mitsuhashi, et al.) shows a multi-pointed punch pin including a discussion of a punching sequence. U.S. Pat. No. 5,463,922 (Mori) shows a roller system for pressing punch pins in a sequence.

Japanese Patent Publication No. 64-087192 (Izumi, et al.) shows a punch pin with elongated cutting points, and a graph showing two force peaks during the punching operation. Japanese Patent Publication No. 61-172629 (Yukio) shows different cutting end profiles for a punch pin, including an asymmetrical end. U.S. Pat. No. 4,829,867 (Neilsen) shows a fixed diameter sleeve type punch pin with a helical cutting end. U.S. Pat. No. 6,688,199 (Godston, et al.) and U.S. Pat. No. 4,077,288 (Holland) disclose punches with a vertically oriented or upright paper slot. In the Godson '199 patent, the surrounding structure532holds the papers away from the user. As illustrated inFIGS. 4 and 9, slot62including floor64and ceiling68are perpendicular to the punch pin axis50.

SUMMARY OF THE INVENTION

It is desirable to minimize the peak forces to cut a hole or holes in papers or other sheet media in a finger- or hand-pressure operated tool or in a compact motorized tool. The shape at the end of the punch pin is important. One approach is to cut the notch so that the pointed cutting ends are at different levels. Then the lowest pointed end cuts into the paper or sheet first before the higher pointed end, so the force required is less than that with two equal elevation ends cutting into the paper or sheet simultaneously. One approach to creating different levels for the cutting points is to locate the notch in between the cutting points off-center. Another approach is to provide an uneven punch base so that the pointed ends cut into the sloped sheet differently.

To further improve the efficiency of a hole punch, the pull out force of the pin must be reduced. One way to reduce the force is to make the hole in the paper larger than the pin diameter. A non-circular inner circumference can make it easier to expand the hole about a circular pin. For example, an oval hole in a sheet with its largest diameter sized greater than the punch pin diameter would allow the punch pin to pull out easily. To create an oval hole with a circular pin, in one embodiment, the base or anvil of the frame should be substantially uneven or angled. The paper flexes out of a flat plane at the anvil. The pin thereby presses the paper at a substantial angle off perpendicular to the punch pin creating a slightly ovoid hole. With such an arrangement, the smaller diameter of the ovoid hole remains equal or smaller than the pin diameter, while the larger diameter of the ovoid hole is larger than the pin diameter. The pin can easily force open the narrow direction of the hole when the paper is repositioned perpendicular to the pin since the loose fitting larger diameter direction can flex toward the pin. The ovoid hole becomes slightly distorted into a round shape that is larger than the simple round hole that is ordinarily made by the pin.

Another approach to ease the pin removal is to use an expanding pin. In such an exemplary embodiment, a thin-walled sleeve includes an angled cutting end. The end is ground to a sharp edge and may cut progressively from one side of a hole toward the opposite side. In a preferred embodiment, the sleeve is formed from a sheet metal blank into a hollow cylinder, and includes a longitudinal gap between the two opposed edges of the formed blank.

The sleeve is expandable whereby it has a larger diameter as it is forced into the paper and a smaller diameter as it is pulled out. The longitudinal gap becomes larger allowing the sleeve to expand. The sleeve at least partially surrounds a punch pin. The punch pin includes a head at the top. Once assembled, the pin is slidable within the sleeve wherein the head is normally spaced above the top of the sleeve. Pressing the pin/sleeve assembly at the pin head into the paper sheet causes the pin to slide down with the head moving toward the sleeve. A groove around the circumference of the pin receives a radially inward facing rib formed in the sleeve, or equivalent structure, so that as the pin slides within the sleeve, the rib slips out of the groove and expands the diameter of the sleeve. During the downward cutting stroke, the expanded sleeve cuts a hole with a larger diameter than the sleeve diameter during the pull out stroke.

An approach to reduce punching effort is to minimize the return spring force. A return spring is commonly used to return the actuation handle back to the start position and to withdraw the punch pin from the punched hole in the sheet material. A first way to achieve a lighter spring force is to reduce the pull out force described above. A lighter spring provides a particular advantage in light duty use, but is also advantageous in any type of punching application. A second way to reduce return spring force is a simplified linkage that enables a user to directly pull out a pin from a punched hole. The return spring may then be just strong enough to retract the pin in most circumstances; the return spring need not be so strong that it can retract the pin under the worst case. Examples of such worst cases include when punching through a very thick stack of papers when the papers have some glue or other contamination, or when the pin has become dull and draws more paper edge into the hole. In such worst case instances, the user can augment the return spring power by pulling up upon an operating handle to retract the pin. Accordingly the spring force may be substantially reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a hole punch element. A hole punch element may be defined as the punch pin, or as the structure within the immediate region of the hole punch device near the pin including the structures that guide the pin and the sheet media or substrate to be punched, such as a stack of papers. For example, a die cast punch support structure may guide pins as well as support an operating handle.

FIGS. 1 to 7show one exemplary embodiment of an improved punch element. Pin20is vertically slidable and guided in frame10along a longitudinal pin axis, depicted as a vertical, dashed line. InFIG. 1, pin20is shown in an intermediate position between an uppermost position and a lowermost position. Lower cutting point21aof pin20is just protruding into anvil cavity13. Upper cutting point21bof pin20has not entered cavity13inFIG. 1.

Tie bar100is linked to pin20. Tie bar100is preferably a side facing “U” channel in the illustrated embodiment. Linkages acting as the tie bar of other shapes aside from a “U” channel are contemplated. In a multiple hole punch, such as a three hole punch, tie bar100actuates three punch elements spaced along a length of tie bar100. Tie bar100links the pins to a further actuating mechanism shown schematically as handle107. Handle107is pivotably attached to frame10, either directly as shown at pivot104or to a housing body (not shown) that supports one or more frames or punch element portions and an actuating lever system. Handle107is also pivotably attached to tie bar100. Some optional sliding motion is allowed at pivot103in the instance that handle107moves by rotation as shown. In the preferred embodiment, handle107can press downward upon tie bar100and optionally pull up on tie bar100via pivot103.

Pin20, tie bar100, handle107or any combination of these components or equivalent structures may be driven not only by direct manual force of a user's hand but also by a motor or by hydraulics. For example, a motor (not shown) may rotate an eccentric cam and the cam selectively engages tie bar100from above to force tie bar100downward as inFIG. 1.

When a user depresses handle107which rotates about pivot104, pivot103translates the rotational handle motion into a vertical translation of tie bar100. Upper wall102of tie bar100presses atop pin20to urge pin20into papers51or other sheet material, as seenFIG. 2. Still inFIG. 2, lower wall104includes recess105formed into the lower edge of tie bar100to at least partially surround lower body portion24of pin20. Spring clip70fits into circumferential groove25of pin20. Lower wall104of tie bar100fits under spring clip70at recess105. With the contacts at pivot103and/or spring clip70, tie bar100can press pin20in a downward stroke in response to a user's pressing action upon handle107. Moreover, as tie bar100is raised by handle107via pivot103, tie bar100also lifts pin20in an upward stroke through the spring clip70linkage at recess105. Therefore, a user may easily lift pin20directly if the pin becomes stuck in a hole that the pin cut into the stack of papers51. This capability contrasts with the conventional light duty hole punch where an operating handle can only press punch pins, but cannot lift the pins since there is no tensile link to the pin to enable a retracting stroke.

The present invention exemplary embodiment provides a much simpler lifting mechanism than, for example, a pin that has a cross drilled hole holding a dowel used to attach the pin to a lifting arm to enable the lifting stroke. Cross drilling a cylindrical pin through its centerline is costly and difficult to manufacture.

InFIGS. 2 and 5, shelf17provides an optional upper stop for spring clip70. InFIG. 2it is seen that shelf17is similar in thickness to lower wall104of tie bar100. As pin20moves up to its upper most position, spring clip70contacts shelf17. A gap remains to allow lower wall104of tie bar100to fit in between ceiling11of frame10and spring clip70. Therefore, if the punch element is removed, for example to change its position from two hole punching to three hole punching, the gap between ceiling11and spring clip70remains so that the punch element can be reinstalled into recess105and linked to tie bar100. The present embodiment thus benefits from quick and easy interchangeability of the punch elements. The gap also helps in initial manufacturing assembly of tie bar100about pin20.

Frame10includes side walls and an opening facing rearward, in the leftward direction inFIG. 5, to create an optional, partially enclosed space. Pin20is therefore exposed rearward in frame10. As best seen inFIG. 5, rearward is defined as the direction in which slot19terminates, which is opposite to the direction toward which slot19opens. This arrangement allows lower wall104of tie bar100to engage pin20using a simple recess105formed in an edge of tie bar100. Accordingly, the aforementioned embodiment provides a punch pin that can be both pressed into and pulled out of sheet media via a simple linkage system.

Another feature of the preferred embodiment is a reduction in force needed to pull out a pin from a hole the pin has made in a stack of papers51. In the embodiment shown inFIG. 2, slot19has upper floor18aand lower floor18a′. Slot19includes anvil cavity13formed in angled section floor18c. Angled section floor18csurrounds or nearly surrounds anvil cavity13. Collectively, the floor sections18a,18a′ and18cform an uneven or stepped punch element floor. Preferably, angled section floor18cis at a slope angle of about 5° to 25° inclusive across a diameter of pin20, including all angles therebetween, relative to generally level floor18aor18a′. According to basic trigonometry, an angle of 25° across the pin diameter corresponds to an elevation change of about 50% of the pin diameter. An angle of 5° corresponds to an elevation change of about 8% of the pin diameter. Alternatively, the uneven or stepped floor may be locally steeper than the given range of 5° to 25°. In such an embodiment, a nearly vertical or entirely vertical region of anvil cavity13can be formed in an area smaller than the diameter of pin20in combination with or in place of the larger-area, 5°-to-25° sloped section floor18c. According to the trigonometric relationship described above, in this smaller area, the elevation change across the pin diameter preferably ranges inclusively from about 8% to 50% of the pin diameter. In still other alternative embodiments, sloped section floor18cmay be angled anywhere from about 2° to 90° inclusive.

The distance between upper floor18aand ceiling18bmay be a paper thickness limit. More generally, the smallest height of slot19can serve as the paper thickness limiter, and inFIG. 2, this is the height at the left side of slot19or the distance between18aand18b. The paper thickness limit defines the capacity of the punch element or hole punch device and restricts the punch element or hole punch device to use with a pre-determined number of sheets of a given thickness paper. The capacity may be selected to match available leverage or pressing force, or for marketing reasons.

Another way to describe the locally angled or stepped section floor is in relation to a paper guide slot in a multi-element hole punch. In such an assembly of a hole punch structure (not shown), two or more punch elements are spaced side-by-side. Each punch element appears as inFIG. 2to provide for separate holes in a stack of papers. Slots19of the two punch elements define the paper guide slot, with co-planar floors18aor18a′ being the bottom of the slot. The paper normally lies in the plane defined by floors18aor18a′. This plane may be called the “slot plane.” This plane may be visualized in its relevant direction by extending the opposed edges of papers51ofFIG. 2. It may be described by a general level for floors of adjacently spaced punch elements that hold the position of papers51as defined by the same position on each punch element, for example, floor18aof each punch element. Angled section18cis therefore described as a bent area local to pin20that is sloped at about 5° to 25° out of plane, or comparably, an elevation change of about 8% to 50% of the pin diameter across pin20. This local bent area in floor18cguides and offsets the paper stack out of the slot plane near pin20when the paper stack is compressed by pin20. In an alternative embodiment, the slot floor may include local arcuate portions to create such an offset.

Notably, the term “plane” is intended to include a non-linear, sloped, and/or arcuate floor for the in and out direction, or left to right inFIG. 1. The “paper path” defined by floor18a,18a′ and angled section floor18cmay alternatively be described as a bent line bisecting the respective pin axes of the multiple elements rather than a bent plane connecting the multiple elements. The paper is bent to follow the uneven or kinked paper path as pins80of multiple punch elements press the paper against respective bases of the elements.

In a conventional, multiple punch element design, the floors define a straight, smooth, and slightly inclined path. In contrast, angled or stepped section floor18cor equivalent structure in the preferred embodiment of the present invention defines an offset, out-of-plane or out-of-line section from the generally straight inclined path to create a local bend in papers proximate to each pin. In the instance of a smooth inclined path, if ceilings18bof the respective elements are at the same level, then the slot height is different for each element. Typically, the smallest height portion of the smallest slot19defines the maximum paper thickness in the multiple-element hole punch device.

As seen inFIG. 2, when pin20presses on papers51held in slot19, the papers are forced to bend to follow the surface contour of angled section18c. As a result, the angled entry of pin20into the papers causes the apparent shape of pin20at the papers to be an oval. The resulting hole created by pin20in papers51is also an oval with its long axis or diameter slightly larger than the actual diameter of pin20.

Optionally, the entire surface of the floor may be angled as with angled section floor18cto form the out of path section. In this embodiment, the formerly level surfaces of floors18and18awould now be sloped. This works best if the floor surface generally underlying the punch element is narrow from side to side to avoid a large elevation change from one side of the pin to the other. That local area generally underlying the pin may span a width of just smaller than the pin diameter to a width of up to about 5 pin diameters. By further extending the size of the angled section of floor18aand18c—higher on the left inFIG. 2and lower on the right—papers51will be offset more than necessary. The extreme offset may be apparent to a user who might find the appearance peculiar, and may hinder the ease with which papers can be fed into slot19. Consequently, the extreme offset requires an excessively tall slot19for clearance, which carries over into undesired increased bulk of the hole punch device.

Similarly, a highly inclined path connecting together multiple punch elements can provide oval holes. However, the resulting slot height at the lowest area of the floor would be unsatisfactory for typical spacing between multiple punch elements. It is thus desirable to have a substantially inclined floor or path, but with a size limited to the immediate vicinity of the pin. With this arrangement can the hole be usefully oval while maintaining a reasonable slot height for all punch elements and surrounding support structures.

The force of adhesion of pin20with the inside wall of the punched hole is reduced when the hole is oval shaped and the pin cross-section is a circle. The benefit is greatest if papers51are tilted from the angled position to a perpendicular position about pin20before the pin is withdrawn. In the angled position, the oval hole remains tightly fit around the pin since the hole was created in this condition. But if the paper is tilted to be substantially perpendicular to pin20, the hole effectively expands to be larger than the pin diameter along the long axis of the oval hole. The short axis remains the same size relative to the pin. As mentioned above, the slope of angle section18crelative to the horizontal floor18ashould preferably be greater than about 5° or the oval shape will be too subtle to be very effective. If the angle is greater than about 25° across the pin diameter, pin20might slide along papers51more than actually cutting through the papers. Also, the pin will be too strongly biased off the pin axis by the angled entry into the papers and might not properly enter anvil cavity13. Through empirical observations, the slope angle is more preferably about 10° to 15° inclusive including all values between the limits and most preferably about 11° to optimize the above-mentioned benefits.

InFIG. 2, floor section18cis angled off the perpendicular with respect to the pin axis, while ceiling18bis horizontal. As pin20is withdrawn in an upward stroke, papers51tend to adhere to the pin. The papers are pulled up against ceiling18b. At this moment, papers51are tilted and re-oriented toward the perpendicular since ceiling18bis perpendicular to the axis of pin20. As a result and as shown inFIG. 6, oval hole50then has a loose fit about the circular cross-section of pin20. In its more flat orientation, oval hole50is generally larger in area than pin20and contacts the pin only at the two tangential areas shown inFIG. 6. The hole is thus easily distorted toward a round shape to fit loosely about pin20, enabling a low force withdrawal of pin20out of the punched hole. A conventional round hole or near-round hole that fits tightly around the entire circumference of the pin has no ability to be distorted for a loose fitment around the pin, other than by stretching or tearing the paper material. Hence, the force needed to withdraw the present invention pin from the punched hole is thus reduced significantly.

An oval shaped pin with an oval anvil cavity13creates an oval hole in a conventional punch device, but unless the hole is actually larger than the pin as disclosed here, there is minimal advantage in reducing pull out force. Thus, in one alternative embodiment, an oval pin (not shown) installed in the assembly ofFIGS. 1 and 2, with anvil cavity13being similarly oval shaped would provide reduced pull out force. In general, it is not required that the pin be precisely round according to the present invention.

The present invention further contemplates an efficient hole punch design that enjoys reduced cutting forces. In particular, it is preferred that the peak forces are reduced. In a preferred embodiment, an asymmetrical cutting end of the pin enables such reduced peak forces. InFIGS. 2 and 4, it is seen that in the asymmetrical cutting end, lower cutting point21acuts papers51before upper point21bby virtue of the cutting points being at different heights or levels. Therefore, the two cutting points21a,21bcut into papers51via different approaches and at different moments in time at any position of pin20. The different engaging cuts of cutting points21a,21breduces the overall peak forces since the peak force is the sum of the forces acting on cutting points21a,21band upper vertex21c, and at a given position of lower point21a, its cutting action occurs when upper point21bis not performing a difficult cutting action. InFIG. 2, lower point21ahas broken through the last page of papers51and entered anvil cavity13. The force from lower point21ais past the break-through peak. At this moment, upper cutting point21bis performing the peak force entry cut. So the required force on pin20is primarily from only one of the two points, namely, upper point21bin the position shown inFIG. 2.

Sequentially, the cutting force peaks when the point21afirst enters papers51, then second point21bengages the papers, and finally when upper vertex21cfirst enters the papers. In the interim, as the intermediate pages are being cut, the force encountered by pin20is lower. As lower point21acuts through the intermediate pages, upper point21benters the first page. The two cutting points meet at upper vertex21c. Upper vertex21cmay be off center as shown inFIG. 4so that the two cutting points are at the respective high and low positions while the angle of the cut notch to make the points is the same to each side of upper vertex21c. Cutting points21aand21bare a specified axial distance from vertex21cto define a groove height. Cutting forces may be minimized if the groove height is preferably at least twice the minimum slot height between floor18aand ceiling18b.

FIG. 3ashows an alternative embodiment pin cutting end. Center point21dprovides an additional cutting point and additional vertices to create an approximate inverted “W” profile as depicted in the drawing. The “W” profile provides a smooth cutting action near the end of a stroke of pin20since the additional vertices are available to shear papers. Also, the center vertex of the “W” profile is preferably slightly off the center axis of pin20. In various alternative embodiments, the “W” profile may be modified with fewer or additional vertices with peaks of uniform or varying amplitudes, creating a serrated surface. The “W” profile ofFIG. 3aoptionally includes asymmetrical outer cutting points21aand21bsimilar to the asymmetrical cutting points21a,21bof pin20shown inFIG. 4.

InFIG. 2, angled floor18cmay serve an additional function to the reduced pin pull out force discussed above. If a symmetrical cutting end is used for pin20where cutting points21aand21bare at the same axial position or height on pin20, the symmetrical cutting points can still cut sequentially, i.e., at different moments in time since the point adjacent to the higher level of floor18a—the left side in FIG.2—cuts first before the other point. Therefore, the use of angled floor section18cprovides reduced cutting force even with symmetrical cutting points. A symmetrical pin may then be used in combination with angled floor18cto provide sequential cutting end action. Or a slightly asymmetrical pin may be used and the angled floor enhances the sequential cutting action.

It is desirable that pin20maintain a fixed rotational position in frame10, especially when the floor of slot19is not perpendicular to the pin axis. With a fixed rotational pin position, a particular cutting point,21ain this example, always faces left inFIG. 2and into the page inFIG. 1where the point is adjacent to the highest part of anvil cavity13. One advantage of a fixed rotational position is to ensure the sequential cutting action described above. InFIG. 2, cutting points21aand21bare held to each side of the step in the floor of slot19. So even if the cutting ends are at the same level, the points still cut in sequence: point21afirst and point21bnext.

In theFIGS. 3 and 4embodiments, pin20has an optional flat outer surface22. Thus, pin20includes a wide, D-shaped transverse cross-sectional area in the portion with flat side surface22where flat surface22transitions to a curved outer surface of pin20. Top hole15of frame10includes substantially flat interior surface16acting as a keyway, as best seen inFIG. 5. Surface16may be slightly arcuate. The respective flats16,22are thus keyed to each other. When assembled together, pin20slides axially in frame10while supported by top hole15and guide hole14. Pin20, however, cannot rotate because the keyed flat side22engages corresponding flat surface16.

In an alternative embodiment, pin20may be keyed to frame10by means of a protrusion fitted to a longitudinal groove of the pin (not shown). For example, top hole15may have an inward extending tab and pin20may have a corresponding longitudinal groove to receive the tab. The keyed flats16,22of the illustrated embodiment are easier to manufacture than a groove machined into a pin since flat22is a single surface extended to connect two edges of the cylindrical outer surface of pin20. Flat surface22can be cut in a direction perpendicular to the pin axis. In contrast, a longitudinal groove or keyway must be milled along the direction of the pin axis increasing manufacturing cost and complexity.

When papers51are incompletely punched, a paper chip can remain attached or dangling from the stack of papers. In the prior art hole punches, this condition often causes a jam; the chip becomes wedged in slot19and the papers cannot be removed from the hole punch device. The present invention, on the other hand, contemplates that if the circular chip is cut in a predetermined direction, this ensures that the chip cannot become wedged.

To illustrate, inFIG. 7, a partially punched stack of papers is shown. Chip53represents the small, stacked, circle of paper that is to be cut out. The individual chips are incompletely severed from the stack of papers and are attached by tabs52dangling the chips. In the exemplary embodiment of the present invention, upper vertex21cis rotationally oriented as shown with the lowest part of vertex21cpreferably positioned away from the open end of slot19, i.e., to the left inFIG. 7. The highest end of vertex21cis thus rotationally oriented nearest tab52. If there is incomplete cutting, tab52is most likely located near the open end of slot19. With this pin20and vertex21corientation, if chip53remains attached to the stack of papers at tab52, papers51can still be forcibly removed from slot19after pin20is raised since tab52cannot catch on any part of pin20or the surrounding hole punch structure. Further, chip53flexes about tab52and swings back in plane with the surrounding paper material as the papers are pulled from slot19, i.e., toward the right inFIG. 7.

On the other hand, if vertex21cwere angled oppositely to that shown inFIG. 7, with the lower part of vertex21clocated nearest to the open end of slot19, then chip53can become jammed after a partial cut. Specifically, the chip edge presses inside anvil cavity13and the chip may bend over into the hole. This can be visualized by assuming papers51are forced to move to the left inFIG. 7(disregarding the terminating left side wall of slot19). Chip53would fold downward into cavity13and backward to effectively double the thickness of the papers. The papers will no longer fit in slot19and will become jammed. Empirical testing has confirmed this jamming behavior.

The cutting end of pin20may comprise different configurations beyond that shown. For example, symmetrical cutting ends may be used. If the floor of slot19were angled as discussed below forFIG. 14, then a symmetrical pin has the same benefit as that discussed forFIG. 7. To provide the anti-jamming benefit, the last area to be cut, and therefore the highest cutting edge of pin20or lowest area of the floor, should be facing at least generally toward the open end of slot19. To maintain this orientation of the cutting edge, a rotational positioning feature such as flats22,16described above may be used.

In summary, there are various possible cutting end designs for pin20including symmetrical and asymmetrical cutting points. These cutting ends may be used with various designs for the angled segments in the floor of slot19such as different angles or shapes as discussed above. For each combination of these variables, an optimum rotational position for pin20may be empirically determined where jamming as described in the preceding paragraph is minimized.FIG. 7shows one such combination and rotational orientation for pin20. In any combination, the structure described at the upper portion of the pin can hold the pin cutting end in a selected orientation as required.

In an alternative embodiment, an expanding sleeve is used to reduce the pull out force of the pin.FIG. 8shows components of a paper punch element according to this alternative embodiment. Housing160includes slot165to fit an edge of a stack of papers. A pin assembly is slidably fitted in chamber164. According to this embodiment, the pin assembly includes two components, central pin120fitted within sleeve110. Pin120at the top end has pin head124with a slightly enlarged diameter and near the bottom groove122formed around the circumference of the pin. Sleeve110has a longitudinal gap115spanning end-to-end and an inward extending rib113formed in the circumference near the bottom thereof.

Normally, pin120is in a rest position with a slightly raised position relative to sleeve110as seen by the space between sleeve top edge114and head lower face124ainFIG. 8A. Also while in the rest position, rib113fits into groove122, and gap115is closed or nearly closed. Pressing down upon pin head124forces sleeve cutting end112into the papers (not shown). The resulting upward axial force on sleeve110and downward force on pin120cause pin120to slide farther down into sleeve110, and the space at edge114is reduced or eliminated. When the space at edge114is reduced or eliminated, continuing to drive down on head124concurrently displaces sleeve110downward.

Groove122of pin120includes top wall123and lower wall126. As pin120slides down within sleeve110, top wall123presses circumferential rib113. The resulting wedge action, as best seen inFIG. 8Bexpands sleeve110into a slightly enlarged diameter. Gap115splits farther open enabling the diametrical increase, as seen inFIGS. 9 and 10. This diametrical expansion via increased gap115ranges between about 1% to 3% inclusive of the sleeve diameter. During the upward, pull out stroke, sleeve110is retained on pin120by rib113engaging groove lower wall126.

Sleeve cutting end112may be continuously angled so that the hole is cut progressively from one side of the hole diameter to the opposite side. Or cutting end112may include two or more cutting points. Sleeve110may be formed from sheet steel, where the sharp cutting edge shown is ground before the sleeve is rolled into the tubular shape shown. The sheet steel preferably has some elasticity or resilience. Thus, as the pin assembly of pin120and sleeve110is pressed through the papers, sleeve110easily expands. When the downward pressure is relieved, sleeve110contracts to its rest position due to springback, forcing pin120upward, restoring space at top edge114, and closing gap115. Sleeve110is then smaller in diameter than the hole it just created in the paper enabling a low friction pull out of the pin assembly from the hole in the paper. By maintaining preferably about a 1% to 3% diametrical enlargement, gap115will not become so large to inhibit cutting action of the lower edge of sleeve110. Lastly, it is contemplated that the locations of the rib and the groove can be reversed so that the groove is formed in the sleeve and the rib is formed in the pin.

FIGS. 11 to 16show an alternative embodiment of the solid-pin based punch element ofFIGS. 1 to 7. In this embodiment as seen inFIG. 15, pin80includes transverse slot84with step83. Frame60includes a hollow interior to fit return spring90. Return spring90is preferably a torsion spring. The spring has upper end91and lower end93and preferably dual coils92. Coils92are positioned remotely from pin80rather than coaxial with or adjacent to the pin as with prior art helical return springs. As illustrated, coils92are housed within an enclosed space of frame60for improved appearance and protection of the spring. Of course, frame60may optionally include openings in front wall65and/or in one or more of the side walls. Face85of pin80contacts edge61of frame60in an uppermost position of pin80(not shown) according to one embodiment of a stop structure.

Upper spring end91engages slot84against step83. As seen inFIG. 12, lower end93fits into recess62of frame60. Lower end93preferably includes an optional bent segment as shown to extend into recess62. Upper end91presses ceiling84c of slot84in pin80. Ceiling84c is optionally angled as shown inFIG. 14so that return spring90is biased to press against vertical shelf83, to the left inFIG. 14. Return spring90therefore provides a lifting bias to pin80, which must be countered by the user during a downward punching stroke of the pin.

In a preferred embodiment, return spring90is a double torsion spring including two substantially concentric coils92, but other spring configurations such as a leaf spring or cantilevered spring can be used. The function of coils92is provided by the helical coiled portion of the spring, where the helical coil for this purpose is the coil of a torsion spring. In the return spring90ofFIG. 16, two arms95are joined by a connecting segment at upper end91. Arms95angle toward each other moving from upper end91toward coils92. Arms95may then wrap circumferentially around a portion of the body of pin80to retain the spring against the pin. This wrapping retention may act in addition to or instead of the angle bias discussed for ceiling84c. Arms95may include further distinct bends (not shown) to more completely surround or wrap pin80from behind the pin. Using the upper and lower fitment of return spring90to frame80as described, the spring is securely held in the assembly.

Torsion spring coils92can store substantial energy in a compact space in contrast to conventional return springs. Such conventional springs have typically been simple compression springs surrounding the pin and pressing a spring clip that is fitted around the pin. With a lower energy helical compression spring as in the prior art, the bias force increases greatly as the pin is pressed downward. But the conventional compression spring cannot fit a large number of coils in the limited space surrounding the pin, and fewer coils mean a higher spring constant k and a stiffer action. An inescapable result of a stiff action is that the force to operate the conventional hole punch is needlessly high as an operating handle is pressed downward toward its limit. This effect is particularly evident when fewer stacked paper sheets are being punched. With conventional hole punches then, most of the effort is used merely to overcome the force of the return spring in many applications. This is best observed by pressing a conventional punch with no papers inserted yet the downward force on the handle is unnecessarily high.

In contrast, torsion spring coils92are positioned remotely from and are not placed coaxially with pin80, as seen inFIG. 14. Arms95of spring90may be relatively long. Then a given pin displacement causes a relatively small angular deflection of coil92resulting in a small increase in spring bias. This is a specific advantage of a torsion spring functioning as a return spring over a helical compression spring fitted coaxially or in parallel to the punch pin.

Optionally, a long, flat bar or other elongated, axially bendable spring may be attached to the punch device at a location remote from pin80and extended to pin80to bias the pin upward out of the punched hole. In still another alternative embodiment, a helical compression type spring may be remotely mounted from pin80with extended upper and lower arms stretching radially from the spring (not shown). More precisely, a helical spring coil may be situated axially parallel along side pin80but not be mounted coaxially to pin80, while the coil terminates in stranded wire arms at respective upper and low ends with the terminal wires extending radially outward toward pin80. Here, the helical spring is not placed primarily under compression but rather bends along its axis during deflection as the extended arms move toward each other with pin80. The bending and biasing action of the helical spring as applied to this embodiment is thus similar to coiled torsion spring90.

As similarly discussed above forFIGS. 1 to 7, pin80is axially movable or slidable in frame60within lower guide opening68and upper guide opening64. The pin is rotatably fixed by flat82of pin80abutting flat66of opening64, as best seen inFIG. 13. For manufacturing efficiency, slot84and flat surface82may extend transversely in a parallel direction as shown.

Pin80is further rotatably positioned by engagement with spring90as described above. The connecting segment at upper end91optionally includes two corners as shown. As spring90wraps around pin80, these two spring corners of upper end91engage step83to hold pin80rotationally. In an alternative embodiment, pin80may be positioned primarily or entirely by engagement with spring90. Other geometries may be used to rotatably link pin80to spring90or other type of return spring. For example, a helical spring may include one or more wires extending radially to engage recesses or slots in a pin and in frame60. Alternatively, a flat leaf spring may contact pin80at an edge of the flat spring.

There are various constructions for linking a punch pin to an actuating mechanism such as a lever or handle. For example, an annular groove on the pin may fit into a slot of an actuating member. However, the groove cannot rotationally secure or immobilize the pin. To address this rotation, the pin may be notched as a keyway to accept an extension or key from the supporting frame. This then rotationally fixes the pin. But such a notch is difficult to cut into the cylindrical surface of a typical pin. A dowel may bisect the pin through a drilled hole in the pin. This can rotationally secure the pin, but again it is difficult to manufacture. In particular, it is a complicated process to drill through a cylindrical part, and tedious to assemble a dowel into such an assembly.

InFIGS. 12 and 14, tie bar200is shown with optional leg201extending into slot84. See alsoFIG. 15. Tie bar200is part of a hole punch device that includes an actuating handle (not shown) similar to handle107ofFIG. 1. The handle is linked to tie bar200to press downward upon the tie bar. The handle is also preferably linked to tie bar200so that the tie bar may be pulled upward through, for example, a linkage shown as lever107inFIG. 1. Other actuating devices may be used to move tie bar200such as a cam, knob, motor, or other user interfaces known in the art. Other configurations for tie bar200may be used as well, such as a “U” channel, “Z” form, a bent rod, or flat form.

As tie bar200presses pin80downward, leg201presses lower horizontal wall84aof slot84. When pulling upward upon pin80, leg201presses upper horizontal wall84bof slot84. As discussed above, return spring90presses ceiling84cimmediately above upper wall84b. The term “slot” is intended to encompass the various structures just described that provide the functions of walls84aand84band ceiling84c. In alternative embodiments, the slot may be in the form of steps, ridges, teeth, serrations, indentations, grooves, or the like. Optionally, ceiling84cand upper wall84bmay be a common surface. Then leg201remains under return spring90, but presses upward on upper end91of spring90directly. Or alternatively, return spring90could be located underneath leg201, and leg201presses lower wall84avia a thickness or diameter of return spring90. Spring90then biases pin80upward through a thickness of leg201.

Slot84and flat82are preferably cut to a depth of about halfway through the diameter of pin80. This provides a substantial surface for the respective actions of flat66and leg201, as seen inFIG. 13. Flat82and slot84may be cut from the same direction as shown so that the terminating wall of slot84and flat82face the same radial direction. Such a structure may be optimal for production since a single machining operation can cut all such features. Alternatively, flat82and slot84may face opposite or different radial directions. Flat82may be modified to include an arcuate portion, curved either along the axial direction (side view) or along the radial direction (end view).

In another embodiment, spring90does not engage an individual pin80. Rather, a return spring acts to bias tie bar200upward. The tie bar in turn biases pin80upward by pressing upper wall84b. The return spring may be a torsion, helical, flat or bar spring.

Tie bar200preferably links to and actuates more than one punch element. Of course, the tie bar may optionally be linked to and operate a single punch element. Lever107ofFIG. 1or like actuating devices operate tie bar200and tie bar200in turn actuates either a single or multiple punch elements. The punch elements are supported by surrounding hole punch structures (not shown). Such structures normally include, for instance, an attachment member to hold the punch element or elements to the device, a linkage to an actuating handle or lever, a ruler with detents for precisely spacing the punch elements a specific distance apart, and a receptacle to receive cut out paper chips.

InFIGS. 11 to 13, frame60includes feed slot69with floor69aand ceiling69b. Floor69amay have a locally angled portion as described in connection withFIGS. 1 to 7. In the embodiment shown inFIG. 12, however, the locally angled portion includes a “V” shaped indentation in floor69ahaving sides67angled off the perpendicular to the pin axis and meeting at vertex67a. The “V” shaped indentation is formed with opposed sides67bending downward from the generally flat surface of floor69a; the legs of the “V” span the area of floor69alocal or proximate to each pin80. In various preferred embodiments, the span of the legs of the “V” shaped indention falls within a range of about just under 10% of the pin diameter up to 5 pin diameters. The indented sides67are partly visible inFIG. 13. InFIG. 12, papers51are deflected out of plane to approximately follow the “V” profile. As pin80is retracted after cutting a hole in papers51, the papers are slightly lifted and flattened against ceiling69b; this lifting and flattening re-orients the angle of the papers in the area of the pin to be approximately perpendicular to the pin's elongate axis.

The punched hole is elongated on each side of the basic circular opening to form an oval shaped hole similar to that shown inFIG. 6. The retraction or pull out force is thus reduced as discussed earlier. Alternatively, the indentation in floor69amay be a “U” shape, a groove, a dip, a channel, a step down or other profile including simply a lowered central area. For best performance, it has been empirically determined that the angle of sides67should be preferably between about 5° to 25° inclusive, including all angles therebetween, relative to the surrounding floor69aor relative to a perpendicular off the pin's elongate axis. In still other alternative embodiments, the angle of sides67may fall within a range of about 2° to 90° inclusive. As discussed forFIG. 2, the preferred angle corresponds to a change in elevation. Across the pin diameter the indented design ofFIG. 12includes half the elevation change compared to a single angled segment for an equal angle of the segments. This is because the angle extends for half the distance, one half the pin diameter according to the current trigonometric relationships. Therefore, to use the figures from the discussion ofFIGS. 1 to 7, the angular range of 5° to 25° corresponds to a vertex67athat is lower than floor69aby a depth ranging from about 4% to 25% of the pin diameter.

Another way to describe the angled floor section is in relation to a paper guide slot in a multi-element hole punch. In an assembly of a hole punch structure (not shown), two or more punch elements like that shown inFIG. 12are spaced side-by-side to provide for separate holes in a stack of papers. Individual feed slots69of the two punch elements collectively define the paper guide slot, with at least one portion of floor69abeing the bottom of the slot. The paper normally lies in the plane defined by a same portion of the floor69aon each spaced punch element. This plane may be called the “slot plane.” The slot plane may be visualized in its relevant direction by the extended direction of papers51inFIG. 12. It is described by a general level for floors of adjacent spaced elements to define the position of papers51. Indented and sloped sides67have a local, approximately 5° to 25° out of plane area or bend near to each pin80. This local slope or bend guides the paper out of plane, or offset, near pin80when the paper is pressed by pin80. The term “plane” is intended to include a non-linear floor for the in and out direction, i.e., left to right inFIG. 11. The path defined by floor69aand indented sides67may alternatively be characterized as a bent line bisecting the respective pin axes of the multiple punch elements rather than a bent plane connecting the multiple punch elements.

A further alternative embodiment of the present invention is shown inFIG. 14. Floor369is angled front-to-back into feed slot69, i.e., side-to-side in the profile view ofFIG. 14or between closed rear end69cof feed slot69and the opposed open front end. The angle of floor369may slope from low to high in the left-to-right direction inFIG. 14to provide a large open front end, or be sloped from high to low (not shown) to provide a small open front end.

Several benefits are realized with front-to-back angled floor369. InFIG. 14, pin80is shown in an intermediate position. In this exemplary embodiment, cutting points21are symmetrical meaning that they are at the same axial position of pin80. However, for the selected rotational position of pin80shown, the cutting points press into the papers (not shown) held in feed slot69in a sequence of right to left due to the angled or sloped floor369. The required force to cut a hole with this symmetrical pin is thereby reduced comparably as with an asymmetrical pin.

A reduced cutting force can also be achieved if the “V” indentation of sides67ofFIG. 12is located off center (not shown) with respect to the pin axis. In such an arrangement, a symmetrical pin presses each side67and then the papers upon the sides67in this sequence. These effects are similar to that discussed earlier for angled floor section18cin connection withFIG. 2. As suggested by the preceding discussion, points of a punch pin may cut in sequence through one or a combination of an asymmetrical pin and/or a non-perpendicular floor of a paper slot with respect to the pin axis. To provide a distinct sequence in pin cutting with a symmetrical pin, the angle of floor369should preferably be greater than about 5°.

Another benefit of inward angled floor369is realized when the punch element is used with feed slot69in a vertical orientation. The angle of floor369makes the full depth of feed slot69more visible to a user when angled floor369optionally tilts toward a user. For example, a punching device may be designed to fit the element in a position rotated 90° clockwise from the position shown inFIG. 14. The device may be designed for use with cutting points21normally facing the user. With this arrangement, feed slot69extends and opens upward. Feed slot69also angles toward the user thus enhancing the convenience for the user. Optional surrounding structures may further guide papers toward and within feed slot69.

In the exemplary embodiment of the present invention inFIG. 14, ceiling69bis perpendicular to the pin axis. Optionally, ceiling69bmay angle in the same direction as floor369to more clearly define an insertion orientation for papers. Or ceiling69bofFIG. 14, or any other illustrated punch element, may angle away from floor369, or69a, to provide a wider opening for feed slot69to facilitate inserting papers. In either of these examples, ceiling69bis not perpendicular to the pin axis.

A still further benefit of angled floor369of feed slot69is that pin80creates an oval hole in papers if the angle off perpendicular from the pin axis is greater than about 5° and less than about 25°. The front-to-back angle of floor369may rise upward toward rear closed end69cas shown inFIG. 14, or floor369may alternatively angle downward toward closed end69c. The cutting and pull out benefits as described are equal. This pin pull-out force reduction is analogous to the force benefits discussed in connection withFIG. 2and side-to-side angled floor18c, and with the indentation with sides67in theFIG. 12embodiment. If ceiling69bis perpendicular to the pin axis, then the pin pull out force is reduced as discussed in connection withFIGS. 2 and 12.

Creating the oval hole using angled base369also allows a sharp angle while maintaining a compact slot height because there is no cumulative increase in height over a long distance. As with angled section18cofFIG. 2or “V” sides67ofFIG. 12, the angle of base369and the associated elevation change are localized to each punch element.

InFIGS. 11 and 14, frame60includes an outer, upper, lead-in surface65that is angled and a lower lead-in surface63. Upper lead-in surface65angles closer to pin80when moving toward a termination at slot69. InFIG. 14, lead-in surface65provides a paper lead-in guide into slot69. Importantly, lead-in surface65is angled for substantially the full height of frame60above slot69. By contrast, conventional punch element frames include such a lead-in surface only as a filleted transition between the paper slot and the outer surface, similar to the area shown inFIG. 11as the corner where upper lead-in surface65joins ceiling69b. But upper lead-in surface65includes an angled or curved profile along most or all of the length of pin80, unlike conventional designs. Indeed, frame60includes lower guide opening68and upper guide opening64. Upper lead-in surface65includes a length parallel to the pin axis extending between near the levels of these respective openings68,64. Along the length of upper lead-in surface65, the surface angles closer to pin80moving from the level of upper guide opening64down toward lower guide opening68. Lead-in surface65may alternatively form an enclosing wall of the enclosed space of frame60as shown. The upper lead-in surface65thus provides an effective guide to help position papers within slot69at the location of the punch element.

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 form the spirit and scope of the present invention. It is therefore intended that such changes and modifications be covered by the following claims.