Hand-Held Fastener Driving Tool

A. Field of the Invention

The present invention relates to improvements in electric fastener driving tools.

B. Description of the Prior Art

Electric tools for driving fasteners such as staples, tacks and the like are well known and widely used. Examples of tools of this character may be found in U.S. Pat. Nos. 3,141,171; 3,172,121; 3,179,866; 3,434,026; and 4,005,812 all assigned to the assignee of the present invention. These tools illustrated in the above-identified patents set forth the basic components of the tool and are incorporated herein by reference.

The prior art tools commonly include a housing that defines a handle portion and a head or nose portion within which a solenoid winding is mounted for accelerating a magnetic armature. Specifically, a control circuit is operated by a switch in the handle portion for energizing the winding. A magazine is carried by the base of the head portion and by the handle for introducing fasteners into a drive track to be driven by a drive blade supported by the armature.

Normally, the armature of the prior art tools is connected to a second armature and to a single cone spring to allow overtravel of the blade and engagement with a bumper. After continued operation of the prior art tool, however, it often occurs that the bumper disintegrates resulting in the armature engaging a portion of the housing destroying the tool.

An additional problem with the typical prior art tool is its inability to be used on different work surfaces. One solution to the problem has been a removable jaw or nosepiece that is secured to the tool and must be removed through the employment of tools in order to secure a different jaw to the workpiece.

Another frequent problem with prior art tools is jamming of fasteners in the magazine assembly requiring complete disassembly of the tool to clear the jam.

One of the important objects of the present invention is to provide a tool which is light in weight, is easily and economically manufactured, and includes relatively few parts requiring a minimum of assembly operations.

Another object of the present invention is to provide a new and improved electric fastener driving tool that includes a nose piece that is removable and reversible to orient a desired workpiece engagement surface on the nose piece to engage the workpiece.

A further object of the present invention is to provide a new and improved magazine for an electric fastener driving tool that is inexpensive to manufacture and accomodates a variety of types of workpieces into which fasteners are driven.

An additonal object of the present invention is to provide a new and improved electric fastener driving tool that includes a magazine assembly that is of a configuration allowing a jam to be easily corrected.

Another object of the present invention is to provide a new and improved return spring and plunger blade assembly that prevent destruction of an electric fastener driving tool upon disintegration of the bumper normally engaged by the plunger.

The present invention is directed to a new and improved electric tool for driving fasteners such as staples and the like. The tool includes a housing that defines the handle, a head, a nose and tail portions. A solenoid is resiliently and firmly mounted within the housing and includes a magnetic armature to which a driver is mounted. The armature includes a double cone spring mounted thereon that functions to allow overtravel of the driver during the driving stroke and to protect against damage of the housing of the tool if the bumper against which the armature engages during the downward stroke disintegrates. In addition, this spring may eliminate the need for such a bumper.

A drive track is defined by a magazine and by a nosepiece or jaw removably connected to the magazine. The jaw is held in position by a spring and includes first and second ends that may be of different configurations to accomodate different types of workpieces.

The tool also includes a magazine assembly with an open bottom exposing the fasteners thereby allowing easy clearing of the jams that may occur in the magazine assembly.

The above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention illustrated in the accompanying drawings wherein:

FIG. 1 is a side view of the tool constructed in accordance with the principles of the present invention;

FIG. 2 is a vertical, cross-sectional view of the tool of the present invention;

FIG. 3 is a partial view of the tool of the present invention with the workpiece engaging jaw partially removed;

FIG. 4 is a bottom, plan view taken along line 4--4 of FIG. 1;

FIG. 5 is a view taken along line 5--5 of FIG. 1; and

FIG. 6 is a view of the pusher used in the tool.

With reference now to the figures and initially to FIG. 1, there is illustrated an electric fastener driving tool designated as a whole by the reference numeral 10 and constructed in accordance with the principles of the present invention. The tool 10 is similar in many respects to the tool disclosed in U.S. Pat. No. 4,005,812. For this reason, this patent is incorporated by reference herein and the well known components of the tool 10 will only be briefly discribed.

The tool 10 is designed for portable hand-held use and includes a housing and body generally designated by the reference numeral 12 that includes a head portion 14 a nose portion 149, a tail portion 150 and a handle portion 16; the latter being adapted to be grasped by the hand of the user of the tool 10. A magazine assembly generally designated by the reference numeral 18 is attached to the tool 10 and is adapted to contain a supply of fasteners that are to be driven by the tool. The nose portion 149 and tail portion 150 include molded projections 151 and 152 for securely attaching the magazine assembly 18 to the housing 12 by fitting through apertures 154, 155 and in the U-shaped frame 110. The head portion 14 of the tool is adapted to contain a solenoid 20 that is held at the bottom by a ring 22 formed on the inner peripheral surface of the head portion 14 and at the upper end by three molded fingers 24, 26 and 28. In this manner, the fingers 24, 26 and 28 provide a resilient biasing force tending to bias the metal cup 30 and the solenoid 20 into engagement with the ring 22 with sufficient force to prevent shaking or movement of the solenoid 20 relative to the tool housing 12 during operation thus preventing damage to the solenoid 20.

The solenoid 20 is electrically connected to a switch 32 that may be actuated by a plunger 34 that is mounted within an aperture 36 in the handle portion 16 of the tool 10. The microswitch 32 is electrically connected to a circuit board 38 that in turn is electrically connected to a power cord 40 mounted in the handle portion 16 of the tool 10 that is adapted to be coupled to a source of electrical energy. The power cord 40 is also grounded with the grounding fastener 42 so as to ground the magazine 18.

The magnetic armature of the solenoid 20 is provided by the magnetic plunger 44 mounted for reciprocal movement within the solenoid 20. A driver blade 46 is secured to the plunger 44 by a roll pin 48. The plunger 44 includes an elongated bore 50 within which a plunger extension in the form of a common fastener or nail 52 is press fit through the employment of knurling 54 of the outer surface of the extension 52.

In accordance with an important feature of the present invention, it is desirable to allow overtravel of the plunger 44 during a driving stroke while preventing destruction of the tool 10. Accordingly, surrounding the plunger 44 and extension 52 is a double cone spring generally designated by the reference numeral 56. The lower or first cone portion 58 of the spring 56 is positioned on top of the fingers 24,26 and 28 formed in the housing 12 of the tool 10. The spring portion 58 defines a truncated cone spring similar to that used in prior art tools; however, the spring 56 differs from the prior art springs in that it includes an upper or second cone portion 60 integrally defined with the first cone spring 58. The upper end of the second cone portion 60 surrounds and is engaged by the head 62 of the nail 52. The bumper 64 is supported by cup 30 as shown in U.S. Pat. No. 4,005,812.

The double cone spring 56 provides two flexure rates allowing substantially unresisted travel of the plunger 44 during a drive stroke until the bumper 64 is engaged by the plunger 44. Thereafter, the spring 56 resists further travel of the plunger 44. To accomplish this dual resistance, the first cone portion 58 is fabricated to be more resilient allowing easy flexing. The second cone 60, however, is more tightly wound and, thus, stiffer allowing less flexing. Accordingly, during the downward movement of plunger 44 and just at or prior to engagement with the bumper 64, the first cone portion 58 is substantially fully compressed. After engagement with the bumper 64, the second cone portion 60 begins to compress and due to its greater stiffness, prevents further travel of the plunger 44. Thereafter, the spring 56 operates to return the plunger 44 and the driver blade 46 to their original at rest position whereupon head 62 of the nail 52 engages the disc bumper 65.

As described, the second cone portion 60 serves as a safety such that if the bumper 64 disintegrates during use, the second cone portion 60 prevents engagement of the plunger 44 with any portion of the housing 12 that could result in destruction of the housing 12. Moreover, the bumper 64 could be completely eliminated with the function of the bumper served by the second cone portion 60.

The tool 10 may be used on different workpieces and includes a feature that allows easy clearing of jammed fasteners. The driver blade 46 travels along a drive track 66 defined in part by the vertical member 68 and the leading edge 70 of the magazine 18. The front portion of the drive track 66 is defined by a nose piece or jaw 72 that is removably mounted in the magazine 19. More specifically, the leading edge 70 of the magazine 18 is adapted to engage and hold the jaw 72. To accomplish this holding or securement of the jaw 72 to the leading edge 70, the jaw 72 includes side flanges 76 and 78 each with slots 80 82. The leading edge 70 is inserted into the slots 80 and 82 aligning the jaw 72 in the magazine 18 and maintaining in position to define the forward portion of the drive track 66.

The side flanges 76 and 78 of the jaw 72 are biased against and engage the magazine 18 through the employment of a spring clip 84. The spring clip 84 is generally U-shaped including a bight portion 86 that engages the jaw 72. The clip 84 also includes legs 88 and 90 that are adapted to extend along the magazine 18. The legs 88 and 90 include detent portions 92 and 94, respectively, that resiliently snap into and are held by apertures 96 and 98 defined on the magazine assembly 18 thus serving to clip or releasably hold the spring clip 84 and the jaw 72 to the magazine assembly 18. If it is desired to remove the jaw 72, the detent portions 92 and 94 can be forced out of the apertures 96 and 98 by the use of the fingers of the user. The bight portion 86 of the spring clip 84 may then be grasped to move the clip 84 out of the magazine assembly 18 to a position whereupon the detent portions 92 and 94 engage flanges 100 and 102 of the magazine 18 preventing further withdrawal. Thereafter the jaw 72 may be grasped by the user and moved such that the leading edge 70 is moved out of engagement with the slots 80 and 82 and then be completely removed from the magazine 18. The removal of the jaw 72 is desirable to allow clearing of the drive track 66 of jammed fasteners. It is also desirable to be able to remove the jaw 72 to allow reversal of the ends of the jaw 72 to select the end that will engage the workpiece. More specifically, in the preferred embodiment illustrated the jaw 72 includes a first end 104 including teeth 106 defined thereon. The end 104 defines a workpiece engaging surface and that may be of any design or configuration depending on which of several workpieces the tool 10 may be used. In the preferred embodiment illustrated, the end 104 includes teeth 106 that may be used for gripping a screen or the like.

The jaw 72 also includes a second end 108 that as illustrated is flat and may serve as the working engaging surface for engaging a flat workpiece, such a board or the like. Other types of jaws 72 may be employed, for example, the end 108 may include a central recess that straddles a wire cable if it is desired to staple or fasten a wire cable to a workpiece.

As can be understood from the above description of the preferred embodiment, the jaw 72 provides the user of the tool 10 with the ability to easily clear a jam and to use the tool on different types of workpieces.

Considering now the magazine assembly 18. The assembly 18 is defined by three different portions that may be integral or of three different parts. More specifically, the magazine assembly 18 includes a U-shaped frame 110 a vertical member 68 that defines a portion of the drive track 66 and; with a bight portion 112 that defines the top or cover of the magazine assembly 18. The magazine assembly 18 also includes two similar track members 114 and 116 that may be integrally defined with the frame 112 or may be separate pieces attached to the frame 112 by techniques well known in the art such as spot welding. The tracks 114 and 116 are also U-shaped including legs of unequal lengths. The shorter legs 118 and 120 of the tracks 114 and 116, respectively, are secured to the inner peripheral sides of the frame 110 or may be integral portions thereof. The longer legs 122 and 124 are not attached to the frame 110 and define support portions that are straddled by fasteners such as staples 126.

The magazine assembly 118 constructed as described above defines an open space 128 between the legs 122 and 124 exposing the crown portions 130 of the fasteners 126. Accordingly, if a jam occurs within the magazine assembly 18, the fasteners 126 are accessible by a tool such as a screw driver without disassembling the tool 10 or the magazine assembly 18 allowing the jam to be cleared with minimum of difficulty. If the jam is not easily cleared, the jaw 72 may be removed from the magazine 18 and the fasteners 126 may be engaged by a tool and forced through the nose portion thus releasing the jam. In addition, the space 128 defined by the magazine assembly 118 may be of sufficient dimension to straddle a wire cable when the tool 10 is employed to fasten the cable to a workpiece.

Mounted within the magazine is a pusher assembly generally designated by the reference numeral 132. The pusher assembly includes a pusher rod 134 that is secured to a pusher lock 136 that includes a detent 138 for being engaged in an aperture 140 defined in the magazine frame 110.

A pusher 142 is slideably mounted on the rod 134 and is biased away from the lock 136 by a spring 144. The pusher 142 may be fabricated from a single piece of material such as a metal plate and is formed with a central bore 146 that surrounds and is supported by the rod 134. The bore 146 is of a sufficient axial length such that the pusher 142 is dimensionally stable on the rod 134 and does not wobble thereon. The pusher 142 also includes wings or ams 148 and 150 that straddle the legs 122 and 124 of the track 114 and 116 and engage the fasteners 126 tending to move them along the tracks 114 and 116 toward the drive track 66 of the tool.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described above.