Staple-Driving Tools

The present invention relates to tools for driving staples and, more specifically, to tackers.

A common characteristic of hand tooks called "tackers" is a spring-impelled staple driver and a manually operated actuator that first charges the spring and then releases a latch to free the staple driver for a spring-impelled stroke.

Most manual tackers (e.g. U.S. Pat. No. 3,948,426, issued to G. M. LaPointe) use a coil spring having a stationary end that bears against the frame. The opposite end of the spring is arranged to operate a staple-driving ram. An actuator first retracts the ram and compresses the coil spring. Then the ram is released to be impelled by the spring. As the ram is released, a recoil impulse develops which absorbs much of the energy stored in the spring. As a result of the waste, an over-size spring is needed for a given useful impulse at the staple-driving ram. In turn, an excessive manual operating effort is required for compressing the spring.

A different form of manual tacker is disclosed in U.S. Pat. No. 2,320,568 issued to J. F. Cavanaugh, in which the driven (lower) end of a coil spring provides the staple-driving impulse (as in LaPointe, supra) but in which the manual actuating means acts at the opposite (upper) end of the spring to compress the spring. In terms of efficient utilization of drive effort, the type of tacker in Cavanaugh is superior to the type represented by LaPointe. However, the Cavanaugh tacker is relatively bulky and requires many parts, and hence is costly to produce. Moreover the Cavanaugh type of tacker involves a staple-driving ram at one side of the staple driver and a pivoted latch at the opposite side. When the latch is levered away from the staple driver, a force is developed that tends to pull the staple-driving ram away from its guide surface and thus out of line with the staple to be driven. Additionally, there is a tendency of the staple driver to be rocked at the moment of release, giving rise to serious wear problems.

A problem has arisen in tackers of hazardous misuse. If a tacker is operated casually, away from an object that is to be tacked, a staple is ejected nonetheless, and represents a sharp emitted missile. The problem has been recognized in the LaPointe patent, supra, but not fully solved. In LaPointe, a safety device projects adjacent the staple-emitting passage. Once the tacker is pressed against a work surface, the safety device is pushed inward and renders the tacker operable. However, if the tacker is then lifted away from the work surface, it is fully operable with all the hazard of a tacker not equipped with a safety device.

An object of the present invention resides in providing a novel staple-driving tool of the type having a spring-impelled staple driver as an improvement in one or more respects over the foregoing, and in providing novel tackers improved in other respects.

In one aspect, the present invention provides a novel tacker of the type exemplified by Cavanaugh, yet simplified, and therefore more economical construction.

In another aspect of the present invention, a novel tacker is provided wherein the release means tends to shift the staple driver toward alignment with its slide guiding means, rather than away from its slide guide means. In a related aspect, a novel tacker is provided wherein a separate mechanically operable latch is replaced by a stationary latch and wherein the staple driver is released by shifting it off its latch and into its released path. Consistency and accuracy are realized by incorporating the stationary latch and the guide surfaces for the staple driver in a common part, thereby avoiding the accumulated tolerances of assembled mechanisms.

In a still further aspect of this invention, a novel tacker is provided having a safety feature that is effective to disable the tacker up to the very moment of release if the tacker is not then pressed against a staple-receiving surface.

The present invention provides additional novel features. Tackers are provided having a more economical frame structure, one that inexpensively provides significant mass at the staple-driving end of the frame and minimizes the mass of the frame where large mass does not help. Tackers are provided having a novel economically produced and applied jacket for introducing varied external designs to cover a standardized mechanism and for avoiding the expense of attractively and smoothly finishing the metal parts of the tacker enclosed by the jacket. Novel tackers are provided having a means for adjusting the staple-driving impact so that the tacker can be set for reduced impact when the work surface is soft and easily penetrated and would be excessively indented by a full impact.

The foregoing and other novel features of the invention are incorporated in the illustrative presently preferred tacker and certain modifications described in detail below and shown in the accompanying drawings. As will be readily understood, certain of the novel features may be utilized without others. The novel features are set forth more fully in relation to the detailed description below and in the claims. Further redundant recitation here of those features is avoided in the interest of clarity and conciseness.

FIG. 1 is a lateral view of a novel tacker embodying features of the present invention, and FIG. 2 is an elevation thereof as seen from the left of FIG. 1;

FIG. 3 is a lateral view, partly in cross-section, of the tacker in FIGS. 1 and 2 with its plastic jacket removed and FIG. 4 is a similar view with the operating handle depressed just prior to release of the staple driver;

FIGS. 5 and 6 are fragmentary views of the tacker as shown in FIGS. 3 and 4, and FIG. 7 is a fragmentary top view, partly in cross-section, of the tacker in FIG. 5 as viewed perpendicular to a spring-compressor bar in FIG. 5;

FIG. 8 is a lateral view, partly in cross-section, of assembled frame parts of the tacker of FIGS. 1-7, and FIGS. 9 and 10 are a top plan view and a left-hand end view thereof, respectively, FIG. 9 being partially in cross-section;

FIG. 11 is a fragmentary elevation like FIG. 3 of a modification;

FIG. 12 is a fragmentary view of the tacker of FIGS. 1-10 as seen from the plane 12--12 in FIG. 3;

FIG. 13 is an enlarged fragmentary view, partly in cross-section, of the novel tacker as seen from the left of FIG. 3 with its work-surface feeler 30b projecting as in FIGS. 1 and 2;

FIG. 14 is a fragmentary vertical cross-section of the novel tacker as seen at the plane 14--14 in FIG. 13, a portion of the plastic jacket being shown in phantom;

FIG. 14A is an enlarged fragmentary view in cross-section like FIG. 14 but at the broken line 14A--14A in FIG. 13;

FIG. 15 is a fragmentary cross-section of the novel tacker at the plane 15--15 of FIG. 13, a portion of the plastic jacket being shown in phantom;

FIG. 16 is an enlarged fragmentary view like FIG. 13, showing the novel tacker with its work-surface feeler elevated due to its contact with a work surface, and FIGS. 17 and 18 are cross-sections corresponding to FIGS. 14 and 15, respectively, of the novel tacker as viewed at the planes 17--17 and 18--18 respectively in FIG. 16;

FIG. 19 is an enlarged fragmentary lateral view of components of the novel tacker as shown in FIG. 4 with the operating spring compressed, just prior to release of the staple driver; and FIG. 20 is an elevation viewed from the left of FIG. 19;

FIG. 21 is an enlarged view of the feeler shown as FIG. 13, and FIG. 22 is an elevation viewed from the right of FIG. 21.

FIG. 23 is a fragmentary view of the plastic jacket of the novel tacker as shown in FIG. 1, to the same scale, the jacker being shown open in its as-molded condition;

FIG. 24 is an enlarged cross-section of a portion of the jacket as seen at the plane 24--24 of FIG. 23;

FIGS. 25-28 are cross-sections of the jacket shown in FIG. 23 as seen at the planes 25--25, 26--26, 27--27 and 28--28, respectively, in FIG. 23;

FIG. 29 is a cross-section of the jacket as seen at the plane 29--29 in FIG. 1; and

FIG. 30 is an enlarged detail of a modified portion of the novel tacker of FIGS. 1-10 and 12-29, viewed as in FIGS. 1 and 3.

Referring to the drawings, a presently preferred embodiment of the novel tacker is shown in FIGS. 3 and 4 with the plastic jacket 10 of FIGS. 1 and 2 removed. The jacket is shown separately in FIGS. 23-29, and is described in detail below.

The tacker of FIGS. 3 and 4 comprises a frame 12 (FIGS. 8-10) formed of two metal parts 14 and 16. Part 14 is a stamping, distinctively made of a simple strip of relatively light-gage metal such as cold-rolled steel. Portions 14a, 14b and 14c of part 14 form a U-shaped unit. Part 16 is united to the free ends of the U-shaped unit, forming a hand hole. Each portion 14a, 14b and 14c is basically a channel of U-shaped cross-section having a web connecting two side walls. Cross-sections of portions 14a and 14b appear in FIGS. 12 and 9, respectively, and an end view of portion 14c appears in FIG. 13.

At the left-hand end of the tacker as seen in FIG. 8, the side walls of the channel portion 14c have turned-in end flanges 14d (see also FIGS. 10, 13 and 14A) against which the leading end of a stick of staples is pressed. The staples are advanced inside frame portion 14c by a spring-biased follower of conventional form (not shown).

Part 16 of frame 12 includes a web 16a (FIGS. 8-10) and two side walls 16b. A tang 16c extending from web 16a overlies the web of frame portion 14a and is resistance-welded to it. Advantageously, an extrusion 16d in tang 16c provides for accurate assembly of parts 14 and 16 in preparation for the weld. A further tang 16e extends at right angles from the lower end of web 16a. Tang 16e is welded to frame portion 14c (FIGS. 10 and 13).

Frame 12 is thus a rigid unit comprising parts 14 and 16. The frame is readily fabricated of two stocks of strip steel. Part 16 can be made heavy and of a wear-resistant grade of steel while part 14 can be made of light-gage steel. The material of the two strips is utilized efficiently, with very little scrap. Mass is provided in portion 16 where it contributes resistance to recoil, and the frame is light elsewhere.

The present construction contrasts prominently with the usual "clam-shell" construction of tacker frames wherein two stampings are formed of a sheet of steel. In that construction, a pair of mirror-image stampings are assembled opposite each other, like the shells of a clam. Large areas are punched out of the stampings to form the hand opening here outlined by U-shaped part 14 and part 16. The blanked-out material of the openings in the clam-shell stampings represents substantial waste. Moreover, since a large mass of hard, wear-resistant material is needed at the staple-driver end of the frame, either the entire frame must be made of heavy, hard steel when it is formed of clam-shell stampings, or additional pieces of hard material must be united as laminations to the clam-shell stampings at the staple-driver end of the frame.

The frame of the present tacker, being formed of strip stock, achieves low manufacturing cost while allowing flexibility in choice of material for each part of the frame. Provision is thus made economically for large mass and hard material only where those qualities are needed, and there is no need to resort to a compromise gage or steel that is lighter than desired at the staple-driver end of the frame and needlessly heavy elsewhere.

FIGS. 3 and 4 show generally the mechanism of the illustrative tacker. The actuating mechanism for compressing coil spring 24 and for releasing the spring-impelled staple-driver (to be described) includes manual level 22 and actuating or spring-compressing bar 18. Actuating bar 18 is formed of a channel having side walls 18a and a connecting web 18b. (See also FIG. 12.) Bar 18 operates between the walls of frame portion 14a about pivots 14e (FIGS. 5-9) which are extruded from those walls. Torsion spring 20 bears down against frame 12 and up against web 18b of bar 18 and is coiled loosely about a pin (if required, but not shown) extending through pivots 14e. Manual lever 22 is generally channel-shaped, having side walls 22a connected by web 22b. Walls 22a flank the walls of actuating bar 18. A bump 18c is struck up from the web 18b of bar 18, defining the operating point of the manual level against the actuating bar. Lever 22 has outward-extruded pivots received in holes 16g of frame part 16. Lever 22 provides leverage acting at bump 18c, thus operating on nearly the full length of actuating bar 18 where these parts are proportioned as shown.

A compression coil spring 24 is confined between a locating protrusion 18e of actuating bar 18 and the lower end wall 26a of a spring container or "box" 26. In the raised configuration of the parts as shown in FIG. 3, spring 24 is precompressed. The degree of precompression is a design consideration. The left-hand end portion 18d of web 18b cooperates with an upstanding portion 26b of box 26. End portion 18d is necked-in and extends through a slot 26c in part 26b (FIG. 20). A portion 26b' of upward projection 26b overlies portion 18d, portions 18d and 26b' serving as a connection to maintain the pre-compression of spring 24.

A staple-driving ram 28 (see also FIGS. 19 and 20) is fixed to box 26 as by rivets. Unified parts 26 and 28 constitute a staple-driving unit or, more briefly, a "staple driver". As seen in FIGS. 7 and 20, the forward or left-hand end of portion 18d of the actuating bar is T-shaped, having shoulders 18d' that extend outward to prevent portion 26b of spring-containing box 26 from accidentally slipping off the end of portion 18d. At all times in the arcuate motion of bar 18 there is clearance between upstanding portion 26b and the outward shoulders 18d'.

Frame part 16 has a pair of turned-in vertical flanges 16h (FIGS. 9 and 13) having parallel spaced-apart vertical edges. Box 26 reciprocates in frame part 16. The sides of this box 26 slide against portions 16i of the side walls 16b (FIG. 15) but box 26 is allowed to tilt toward and away from flanges 16h for a purpose discussed below. The downward pressure of spring 24 on box 26 produces clockwise bias on unit 26, 28 (as seen in FIG. 3) that presses ram 28 against the aligned inner surfaces of flanges 16h and of turned-in flanges 14d (see FIGS. 10, 11 and 14A for example) at the staple-driving end of frame portion 14c.

In use, manual lever 22 and frame part 14a are gripped by the user. Lever 22 is forced downward, driving bar 18 downward until a staple has been driven. During most of this motion box 26 is arrested, while compression builds in spring 24. Portion 18d of the actuating bar moves downward in slot 26c (FIG. 20) in the upward-extending portion 26b of the spring-containing box 26.

The parts are shown in FIG. 4 in their configuration just before box 26 is released. After release of the staple-driving unit, the front surface of staple-driving ram 28 slides in contact with flanges 16h and with turned-in end portions 14d of frame portion 14c.

As seen in FIGS. 8, 9, 14, 14A and 15, abutments 16i are struck inward from the side walls 16b of the frame. As noted above, these abutments provide side guides for box 26. The upper edges 16i' of those abutments form latches. Box portion 26b (FIG. 20) has shoulders 26d at the lower edges of wings 26d'. Shoulders 26d bear against latches 16i' after manual lever 22 is depressed very slightly. Box 26 has a rightward tilt at this time. This latched configuration of box 26 and frame part 16 endures until the moment of release.

The presently preferred manner of release of the staple driver comprising box 26 and staple-driving ram 28 may now be described in connection with FIGS. 5-7 and 14A. Compression builds up in spring 24 as bar 18 swings to the position in FIGS. 4 and 6 from that in FIGS. 3 and 5. FIG. 7 shows actuating bar 18 as seen from above and at a slight angle to FIG. 5.

An elongated opening or slot 18f is formed in the walls of actuating bar 18, which receive cylindrical pivots 14e. In the normal, at-rest condition of the parts as shown in FIG. 5, coil spring 24 biases bar 18 to the left (as more fully explained below) so that pivots 14e are pressed against the right-hand ends of slots 18f.

Downward operation of manual lever 22 and actuating bar 18 causes bar 18 to move in an arc about pivots 14e. This occurs until shoulders 18g engage upward extension 26b of the spring-containing box which is latched (FIG. 14A) by abutments 16i. As downward movement of bar 18 continues after shoulders 18g engage upward extension 26b, the spring-container remains latched and in tilted position due to friction at latches 16i' and shoulders 26d of wings 26d' (FIGS. 13 and 14A), causing bar 18 to shift to the right until the left-hand ends of slots 18f bear against pivots 14e. Thereafter, bar 18 moves arcuately and its shoulders 18g (FIG. 6) force box extension 26b toward the left. The front of the box becomes essentially vertical and parallel to frame flanges 16h. Referring to FIG. 14A, wings 26d shift off latch surfaces 16i' of abutments 16i, releasing staple-driving unit 26, 28 for spring-impelled operation. At the end of the staple-driving stroke of unit 26, 28, spring 24 has become extended but not so far as to cause part 26b' to strike projection 18d of bar 18. Just before that occurs, box 26 strikes a rubbery bumper 29.

Both before and after release of the staple driver 26, 28, coil spring 24 bears downward on the bottom of box 26, providing a clockwise bias acting to press ram 28 (FIG. 14A) against frame parts 16h and 14d. After the instant of release, wings 26d slide along guide surfaces 16i" of abutments 16i. The same clockwise bias of spring 24 acting on the bottom of box 26 also acts to cause wings 26d' to bear against guide surfaces 16i" during this sliding motion. The construction assures consistent performance among many of these tackers despite normal tolerances of the parts. Notably, each flange 16h at the front of staple driver 26, 28 is formed in the same part (frame part 16) as guide surfaces 16i" on abutments 16i. Therefore, in production of many of these tackers, guide surfaces 16h and 16i" will have a consistent and accurate relationship, without concern for assembly tolerances.

As a further advantage of this construction, there is no tendency of the latch-releasing operation to draw the staple-driver away from its guiding surface aligned with the staple in driving position.

As a further advantage of this construction, there is inherent assurance of guiding the staple driving unit along its guide surfaces with only a small (if any) angle between the sliding parts. The relationship is readily maintainable consistently in producing these tackers. The relationship also avoids a serious wear condition that is common among many known tackers in which the staple driving unit impacts against a guide surface at the moment of release.

Following a staple-driving operation, manual lever 22 is released by the user for spring-actuated retraction. Actuating bar 18 is swung upward initially by spring 24, raising lever 22 accordingly until projection 18d engages portion 26b' of the spring container 26. This connection maintains the initial precompression in spring 24.

As bar 18 continues to swing upward, operated by torsion spring 20, it carries parts 24, 26 and 28 up as a unit. Staple driver 26, 28 is constrained to move essentially vertically due to the engagement of its wings 26d' with guide surfaces 16i". During this swinging motion of bar 18, the upper end of spring 24 draws bar 18 to the left until pivots 14e engage the right-hand extremities of slots 18f. Thereafter as spring 20 continues to raise bar 18, the upper end of spring 24 is forced toward the right during the purely arcuate motion of bar 18. However the lower half of spring 24 is constrained by box 26 to be essentially vertical, due to its engagement with the right-hand wall of the box. Consequently the upper half (approximately) of spring 24 is forced to tilt to the right. Sidewise pressure of the spring 24 against box 26 between the ends of the spring presses wings 26d' against guide surfaces 16i". As soon as box 26 is raised high enough for wings 26d' to clear abutments 16i, spring 24 shifts the staple driver 26, 28 sidewise, snapping wings 26d' into position over latch surfaces 16i'. Upward movement of bar 18 continues (as limited by manual lever 22) until a limited clearance develops between latch surfaces 16i' and wing shoulders 26d. Subsequently when a staple is to be driven, spring 24 provides a bias that assures the latching cooperation of the wings 26d' with abutments 16i.

The described actuation of the upper end of spring 24 downward by bar 18 has distinct advantages over tackers that lift the lower end of the impelling spring of the staple driver prior to latch release. At the moment of release of the staple driver in any tacker, its sudden motion develops a reverse-acting recoil impulse in spring 24. That recoil impulse is applied to bar 18 in the illustrated tacker. The user's hand bears against lever 22, acting almost directly over bump 18c. Thus, the user's hand inherently provides a downward force that is actually in effect at the very instant that the upward recoil impulse develops. The resistance to that impulse provided by the user's downward pressure is effectively converted into augmented staple-driving effort. One result is that a weaker spring can be used to achieve equal drive effort as compared to tackers of the type in which the spring is both compressed and released from the same end. Conversely, for tackers of both types having equal springs with equal amounts of precompression, the present tackers deliver greater staple-driving effort.

As an alternative to reliance on shoulders 18g to effect release of shoulders 26d from the latch surfaces 16i', indeed as a supplement to assure such release, manual lever 22 in the modification of FIG. 11 is provided with a cam 22d that cooperates with upstanding portion 26b of the staple-driving unit 26, 28. Cam 22 pushes wings 26d' off latch surfaces 16i' after the desired build-up of compression in spring 24. Either of the described forms of release are effective, and both may be used together.

The illustrative tacker thus far described is useful and complete. However it is here equipped with a safety device which, were it omitted, would not impair the performance of the tacker per se. This feature suppresses operation of the tacker at all times except while it is being pressed against a staple-receiving object, up to the very moment of release of the staple driver. This feature is described in reference to FIGS. 13-18. (In FIGS. 3 and 4, the scale is too small for the safety device to be shown as part of the mechanism.)

The safety feature is imparted to the illustrative tacker by including interposer or feeler 30. Feeler 30 of resilient metal (FIGS. 21 and 22) includes a long, thin and narrow body portion 30a with marginal stiffening flanges 30a' along most of its length. Body portion 30a extends downward to a projecting portion 30b (see FIG. 3) and extends upward to form a two-walled interponent 30c. Leaf springs 30d integral with feeler 30 flank body portion 30a near its lower end.

FIGS. 13-15 represent the tacker with feeler portion 30b projecting, as in FIG. 3. Leaf springs 30d act against turned-in lips 16f of the tacker's frame. Body portion 30a of the feeler is received loosely between turned-in flanges 16h of the frame, in front of the unit 26, 28 and within the plastic jacket 10. The lower end portion of feeler 30 is received between jacket 10 and turned-on lips 14d of the frame (FIGS. 9, 10, 13 and 14). Unit 26, 28 is elevated, and actuating bar portion 18d bears against the top of slot 26c in spring-containing box 26. Staple S (FIG. 13) is in the drive position below driver 28. Staple S is part of a stick of staples supported on rail 32 and biased (by a conventional staple-stick pusher, not shown) against turned-in lips 14d. Rail 32 has flanges united to opposing flanges 14c of frame part 14c. Sticks of staples may be loaded onto rail 32 at the end remote from the staple-driving unit.

Notably, with feeler 30 projecting as in FIGS. 13 and 14, interponents 30c are located in the space between the front surface of the spring container and the rear or inner surfaces of flanges 16h. Interponents 30c are here shown as straddling staple driver 28.

In this condition, it will be recognized that the tacker cannot be operated to drive a staple because unit 26, 28 is tilted back a bit, with its shoulders 26d (FIG. 20) arrested on the top latching edges 16i' of abutments 16i. Release of the staple-driving unit is prevented by the interponents which block releasing movement of the unit 26, 28 from its latches. Thus, there is virtually no way to "tease" the tacker by preliminary manipulation without the feeler being depressed at the moment of release of the staple-driving unit. Consequently, the tacker cannot be used thoughtlessly to eject a staple as a missile into open space.

FIGS. 16-18 correspond to FIGS. 13-15, but show the mechanism with feeler portion 30b' pressing against a staple-receiving work piece W, in the elevated position of the feeler. Interponents 30c are raised out of cooperation with turned-in lips 16h of the frame. Consequently the feeler is in no condition to interfere with the forward tilting of the staple-driving unit 26, 28. Shoulders 26d can readily be shifted off abutments 16i by operation of shoulders 18g of actuating bar 18 (FIG. 7) or by operation of cams 22d (FIG. 12) for releasing the staple driver.

Plastic jacket 10 virtually encloses the tacker. By providing this jacket, numerous problems are avoided. Electroplating many metal parts for improved appearance and for protection against corrosion becomes unnecessary, and the design of the operating parts is not complicated by consideration of their appearance if (otherwise) they were to be exposed to view. Notably, the entire tacker can be restyled readily to create varied impressions on the buyer. In that way, several designs of jacket can be used with the identical mechanism. Different custom designs can be used to identify a variety of proprietary tackers with each of several distributors.

The tacker construction as described above is economically contained in a one-piece molded plastic jacket 10 shown in FIGS. 23-29. The jacket is molded "open" or basically flat, and it is adapted to be wrapped around the front (the left-hand end of the tacker as in FIG. 3) and then permanently secured in place. In FIG. 23, jacket 10 comprises a central panel 10a having thinned side margins 10b (FIGS. 23 and 25) acting as hinges to join panel 10a with sides or wings 10c and 10c' of the jacket. Each side 10c, 10c' includes a vertically elongated panel 10d and right-angled portions 10e (FIG. 25). Each wing 10c, 10c' also includes portions 10f that complement part 14 of the frame. As seen in FIG. 24, the lower length 10f-4 and the upper length 10f-5 and the rear length 10f-6 each has an edge 10f-1 that abuts a like edge of the other wing. Lower length 10f-4 of each wing has a groove 10f-2 that receives the opposed and united flanges of frame part 14c and staple-supporting rail 32 (FIG. 13). A further slot 10f-3 in lower length 10f-4 of wing 10c is provided for accommodating a projecting finger piece on a spring-biased pusher (not shown) for a stick of staples on rail 32. The upper lengths 10f-5 and the rear portions 10f-6 (right-hand end in FIG. 1) are complementary to frame portions 14a and 14b, respectively. Aside from slot 10f-3, wings 10c, 10c' are mirror-image counterparts of each other.

In assembling jacket 10 to frame 12, the front panel 10a of the jacket is first pressed against turned-in flanges 16h at the left end of the frame and wings 10c and 10c' are bent about hinges 10b against the opposite sides of frame parts 16 and 14. Flaps 10i extending from panels 10d of the jacket fit against side portions 16b of the frame. Cupped portion 10g of the jacket is then swung as a cap over the upper ends of frame portions 16b. Side walls 10g-1 of the cupped portion enclose flaps 10i (FIGS. 23 and 26).

Wings 10 advantageously have complementary small knob-and-socket "poppet" formations along the abutting edges of wing portions 10f-4, 10f-5 and 10f-6. Such complementary interlocking formations may be located judiciously, as at points 10j in FIG. 30 (sheet 1). They snap together and hold the abutting edges against each other.

The jacket is more permanently held in place by cement applied to flaps 10i and to the abutting edges 10f-1. No holding clamps or fixtures are needed to hold the jacket while the cement sets, where the interlocking formations are used. Flanges 14b' of frame part 14 (FIGS. 8 and 9) are received in mating channels 10k (FIG. 23) as a further means for locking jacket 10 in place.

It was explained above in connection with FIG. 7 that shoulders 18g of the actuating bar operate to release or unlatch the staple driver 26, 28. That occurs when ample stored energy has developed in spring 24. The release point may be made adjustable.

It may be desirable to reduce the driving effort of the tacker, as when working on easily-indented material that can assuredly be penetrated by staples using less driving impact. FIG. 30 illustrates an adjustment that may be readily incorporated into the tacker described above for reducing the staple-driving effort of unit 26, 28. Release of staple driver 26, 28 is adjusted to occur earlier in the spring-charging stroke of lever 22. For this purpose, a bushing 34 is fixed to the opposite walls of frame portion 14a, and a screw 36 is threaded into the bushing. Aperture 10m in modified jacket 10A provides access to screw 36 for making the adjustment. The screw abuts and operates a movable pressure plate 38 that has projections slidably captive in rectangular holes in the walls of frame portion 14a. Plate 38 replaces the left-hand ends of slots 18f as the compression bar 18, becoming effective as lever 22 nears the end of its stroke. For maximum staple-driving effort, plate 38 can be adjusted so that part 26b becomes unlatched from (is pushed off) abutments 16i due to coaction of the left-hand end of slots 18f with pivots 14e. Adjustment of plate 38 for earlier coaction with actuating bar 18 causes release or push-off of unit 26, 28 earlier in the operating stroke of the manual lever 22 when less-than-maximum build-up of the spring energy has developed. This is one way to provide for ample staple-driving impact for heavy work while rendering the tacker adaptable to conditions where less impact is wanted. In the embodiment of FIG. 11, the same effect is realized by forming pivot 16g of the handle as an eccentric whose adjustment changes the unlatching point variably in relation to the spring-compressing stroke of the handle.

As a general comment, the accompanying drawings are to scale. However, the thicknesses of a number of parts are not faithfully represented in some instances. Frame part 16 is of heavy stock and spring containing box 26 is of somewhat lighter gage. Both of these parts are intended to be relatively massive to contribute inertia that resists an initial recoil impulse and to contribute to the staple-driving impulse. Frame part 14, including its portion 14d, are of much thinner stock than either of elements 16 and 26. Staple-driving ram 28 is quite thin, being slightly thinner than a staple to be driven and much thinner than frame part 14.

The nature of the invention in its various aspects has been expressed in connection with the presently preferred illustrative embodiment and modifications. Other embodiments of the invention may readily be devised by those skilled in the art, and certain of the novel features may be used without others. Consequently, the invention should be construed broadly in accordance with its true spirit and scope.