Gas spring fastener driver

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/347,230 filed on Jun. 8, 2016, the entire content of which is incorporated herein by reference.

[0002] The present invention relates to power tools, and more particularly to gas spring fastener drivers.

[0003] There are various fastener drivers used to drive fasteners (e.g., nails, tacks, staples, etc.) into a workpiece known in the art. These fastener drivers operate utilizing various means (e.g., compressed air generated by an air compressor, electrical energy, flywheel mechanisms) known in the art, but often these designs are met with power, size, and cost constraints.

[0004] The present invention provides, in one aspect, a fastener driver including a main housing, a drive blade movable from a retracted position to a driven position for driving a fastener into a workpiece, and a gas spring mechanism for driving the drive blade from the retracted position to the driven position. The gas spring mechanism includes a piston movable between a retracted position and a driven position. The fastener driver also includes an extensible cylinder for moving the drive blade from the driven position toward the retracted position. The extensible cylinder includes a cylinder housing coupled one of the main housing or the drive blade, and a rod coupled to the other of the main housing or the drive blade. A vacuum is created in the cylinder housing for biasing the drive blade toward the retracted position.

[0005] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.

[0016] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0017] With reference to FIGS. 1-7, a gas spring fastener driver 10 for driving fasteners (e.g., nails, tacks, staples, etc.) into a workpiece is shown. The fastener driver 10 includes a main housing 12 (12a in FIG. 9), a nosepiece 14 extending from the main housing 12, and a magazine 18 for sequentially feeding collated fasteners into the nosepiece 14 prior to each fastener-driving operation. The fastener driver 10 also includes a drive blade 22, a tip 26 of which is received within the nosepiece 14, and an onboard gas spring mechanism 30 for driving the drive blade 22 from an initial retracted position (shown in FIGS. 1 and 2) toward a driven position coinciding with ejection of a fastener from the nosepiece 14. Accordingly, the fastener driver 10 does not require an external source of air pressure or other external power source for driving the drive blade 22.

[0018] With reference to FIG. 1, the gas spring mechanism 30 includes a cylinder housing 34 in which a pressurized gas (e.g., air) is stored and a piston 38 protruding from the cylinder housing 34. The pressurized gas biases the piston 38 toward a driven position (shown in FIGS. 3 and 4) in which it is fully extended from the cylinder housing 34. The piston 38 includes a distal end 42 against which a head 46 of the drive blade 22 is abuttable when the drive blade 22 is in the retracted position (shown in FIGS. 1 and 2). Movement of the drive blade 22 is limited to axial reciprocation, between the retracted position and the driven position, by parallel guide rails 50 along which the head 46 of the drive blade 22 is slidable.

[0019] With reference to FIGS. 1-7, the fastener driver 10 also includes an extensible cylinder 54 for raising the drive blade 22 from the driven position toward the retracted position. In the illustrated embodiment of the fastener driver 10, the extensible cylinder 54 includes a cylinder housing 58 affixed to the main housing 12a such that the cylinder housing 58 is stationary relative to the main housing 12a and the cylinder housing 34 of the gas spring mechanism 30. The cylinder housing 58 of the extensible cylinder 54 may be affixed directly to the cylinder housing 34 of the gas spring mechanism 30, or directly to the main housing 12a. Alternatively, the cylinder housing 58 of the extensible cylinder 54 may be affixed to an intermediate component of the fastener driver 10 which, either directly or indirectly, is affixed to the main housing 12a. In some embodiments, the cylinder housing 58 may be coupled to the drive blade 22.

[0020] The extensible cylinder 54 also includes a rod 62 coupled to the head 46 of the drive blade 22 for movement with the drive blade 22. In the illustrated embodiment of the fastener driver 10, the rod 62 is abutted against a flange 66 (FIG. 1) extending in a lateral direction from a longitudinal axis 70 of the drive blade 22, and secured to the flange 66 using a fastener (e.g., a screw). Alternatively, the rod 62 may be affixed to the head 46 of the drive blade 22 using a welding process, adhesives, an interference fit, or by integrally forming, for example. Accordingly, the rod 62 is axially movable between a retracted positions coinciding with the retracted positions of the piston 38 and the drive blade 22 (shown in FIGS. 1 and 2), and an extended position coinciding with the driven position of the drive blade 22 (not shown). A longitudinal axis 74 of the extensible cylinder 54, therefore, is oriented parallel with the longitudinal axis 70 of the drive blade 22. Alternatively, the rod 62 may be coupled to the main housing 12a. Specifically, if the cylinder housing 58 is coupled to one of the main housing 12a or the drive blade 22, the rod 62 is coupled to the other of the main housing 12a or the drive blade 22. In some embodiments, the orientation of the extensible cylinder 54 may be flipped, such that the cylinder housing 58 may be coupled to the drive blade 22 and the rod 62 may be coupled to the main housing 12a.

[0021] With reference to FIG. 8, the cylinder housing 58 of the extensible cylinder 54 includes an interior chamber 78 in which the rod 62 is slidable. The rod 62 includes a piston 82 that divides the interior chamber 78 into a first variable volume region 86 and a second variable volume region 90, the length of each of which is variable and dependent upon the axial position of the rod within the cylinder housing 58. The cylinder housing 58 includes an aperture 94 at one end thereof to fluidly communicate the first variable volume region 86 with an interior of the main housing 12a, which is exposed to atmospheric pressure. In the illustrated embodiment of the fastener driver 10, the aperture 94 is coaxial with the rod 62. Alternatively, the aperture 94 may be radially oriented relative to the longitudinal axis 74 of the extensible cylinder 54. The rod 62 extends through the opposite end of the cylinder housing 58, with the second variable volume chamber 90 being exposed to the atmospheric pressure in the interior of the main housing 12a.

[0022] With continued reference to FIG. 8, the aperture 94 includes a diameter D. During a firing stroke of the drive blade 22 (to which the rod 62 is affixed), the rod 62 is accelerated quickly from its retracted position (shown in FIGS. 1, 2, and 8) toward the extended position, thereby expanding the volume of the first variable volume region 86 in a relatively short time period. The diameter D of the aperture 94 is sized to restrict, but not prohibit, the flow of replacement air into the first variable volume region 86 during this period of expansion. Accordingly, a vacuum (i.e., an absolute pressure less than atmospheric pressure) is created in the first variable volume region 86 as the rod 62 is extended. Because the second variable volume region 90 is exposed to atmospheric pressure, no back-pressure is exerted on the rod 62 during extension.

[0023] In another embodiment of the fastener driver 10, a one-way valve (not shown) may be substituted for the aperture 94 to prevent the flow of replacement air into the first variable volume region 86 during extension of the rod 62 relative to the cylinder housing 58, thereby creating a vacuum in the first variable volume region 86. When the rod 62 is retracted into the cylinder housing 58 to the position shown in FIGS. 1 and 2, any pressurized air within the first variable volume region 86 (i.e., air pressurized above atmospheric pressure) is discharged through the aperture 94 and the one-way valve into the interior of the main housing 12a. Such a one-way valve may be, for example, a ball check valve.

[0024] As is described in further detail below, between two consecutive firing operations of the fastener driver 10, the extensible cylinder 54 returns or raises the drive blade 22 from the driven position (coinciding with ejection of a fastener from the nosepiece 14) to an intermediate position (shown in FIGS. 5-7) between the driven position (not shown) and the retracted position (shown in FIGS. 1 and 2). The fastener driver 10 further includes a lifter mechanism 98, shown most clearly in FIGS. 2, 6, and 7, that completes the return of the drive blade 22 by raising the drive blade 22 from the intermediate position to the retracted position. In the illustrated embodiment of the fastener driver 10, the lifter mechanism 98 includes an electric motor 102 powered by an on-board power source (e.g., a battery), a rotatable cam lobe 106, and a transmission 110 interconnecting the motor 102 and the cam lobe 106. The transmission 110 includes a planetary gear train 114 connected to an output shaft of the motor 102 and an offset gear train 118 connected to the output of the planetary gear train 114. Specifically, the offset gear train 118 includes a small-diameter gear 122 connected with the output of the planetary gear train 114, a large-diameter gear 126 connected with the cam lobe 106, and a chain (not shown) interconnecting the gears 122, 126. Accordingly, torque from the motor 102 is transferred through the planetary gear train 114 and the offset gear train 118, causing the cam lobe to rotate about a rotational axis 130 of the large-diameter gear 126 (FIG. 2).

[0025] With reference to FIGS. 2, 6, and 7, the drive blade 22 includes a follower 134 engaged with the cam lobe 106 while the drive blade 22 is raised from the intermediate position to the retracted position. In the illustrated embodiment of the fastener driver 10, the follower 134 is configured as a cylindrical pin that is slidable along the outer periphery of the cam lobe 106 in response to rotation of the cam lobe 106. Alternatively, the follower 134 may be supported within the head 46 of the drive blade 22 by a bearing, thereby permitting the follower 134 to rotate relative to the head 46. With this arrangement, the follower 134, when configured as a cylindrical pin, may roll along the outer periphery of the cam lobe 106 in response to rotation of the cam lobe 106. Furthermore, the follower 134 protrudes from the head 46 of the drive blade 22 in a lateral direction relative to the longitudinal axis 70 of the drive blade 22, and the cam lobe 106 is positioned between the drive blade 22 and the large-diameter gear 126 of the offset gear train 118.

[0026] In operation of the fastener driver 10, a first firing operation is commenced by the user depressing a trigger (not shown) of the fastener driver 10. At this time, the drive blade 22 and the piston 38 are held in their retracted positions, respectively, by the cam lobe 106 (shown in FIGS. 1 and 2). Shortly after the trigger being depressed, the motor 102 is activated to rotate the cam lobe 106 in a counter-clockwise direction about the rotational axis 130 from the frame of reference of FIG. 2. Upon the follower 134 sliding off the tip of the cam lobe 106, the pressurized gas within the cylinder housing 34 expands, pushing the piston 38 outward from the cylinder housing 34 and accelerating the drive blade 22 toward its driven position. The cam lobe 106 is accelerated to a sufficient rotational speed to prohibit subsequent contact with the follower 134 as the drive blade 22 is being driven from its retracted position to the driven position. In addition, the timing of the drive blade 22 reaching its intermediate position coincides with the follower 134 passing alongside a flat segment 138 of the cam lobe 106 (shown most clearly in FIG. 4), thereby creating an unobstructed path for the follower 134 as the drive blade 22 is displaced from its intermediate position toward its driven position (not shown).

[0027] After the piston 38 reaches its driven position (shown in FIGS. 3 and 4), the head 46 of the drive blade 22 separates from the distal end 42 of the piston 38 (coinciding with the intermediate position of the drive blade 22), ceasing further acceleration of the drive blade 22. Thereafter, the drive blade 22 continues moving toward its driven position at a relatively constant velocity. Upon impact with a fastener in the nosepiece 14, the drive blade 22 begins to decelerate, ultimately being stopped after the fastener is driven into a workpiece.

[0028] During the period of movement of the drive blade 22 from its retracted position (shown in FIGS. 1 and 2) to its driven position (not shown), because the rod 62 of the extensible cylinder 54 is affixed to the head 46 of the drive blade 22 for movement therewith, the rod 62 is also pulled from the cylinder housing 58. As the rod 62 is pulled from the cylinder housing 58, a vacuum is created within the first variable volume region 86 because the rate at which the volume of the first variable volume region 86 expands exceeds the volumetric flow rate of replacement air drawn into the first variable volume region through the aperture to “fill” the expanded volume. After movement of the drive blade 22 is stopped following the conclusion of the first firing operation, a pressure imbalance acting on the rod piston 82 applies a force on the rod 62, causing it to retract into the cylinder housing 58. Because the rod 62 is affixed to the head 46 of the drive blade 22, the drive blade 22 is raised from its driven position toward the intermediate position. At this time, the rotation of the cam lobe 106 is either momentarily stopped or substantially slowed to allow the follower 134 to pass alongside the flat segment 138 of the cam lobe 106 as the drive blade 22 approaches the intermediate position.

[0029] Coinciding with the drive blade 22 reaching the intermediate position, rotation of the cam lobe 106 (in the same counter-clockwise direction) is resumed (or alternatively accelerated if previously slowed) to once again contact the follower 134 (shown in FIGS. 6 and 7). As the cam lobe 106 continues its rotation, the follower 134, the drive blade 22, and the piston 38 are displaced upward from the intermediate position of the drive blade 22 shown in FIGS. 5-8 toward the retracted position shown in FIGS. 1 and 2. At this time, the rod 62 is also retracted into the cylinder housing 58, purging air from the first variable volume region 86 to the interior of the main housing 12a via the aperture 94. The cam lobe 106 continues to raise the drive blade 22 and the piston 38 until both reach their retracted positions shown in FIGS. 1 and 2, at which time the first firing operation is completed. Thereafter, additional firing operations may be initiated in a like manner.

[0030] In an alternative firing cycle, the lifter mechanism 98 may remain deactivated after the extensible cylinder 54 has returned the drive blade 22 to its intermediate position, thereby maintaining the piston 38 in its driven position shown in FIGS. 6 and 7, until the user depresses the trigger to initiate a firing operation. This way, the gas spring mechanism 30 remains in a deactivated state (i.e., with the piston 38 in its biased, driven position) when the fastener driver 10 is not in use.

[0031] By providing the extensible cylinder 54 to return the drive blade 22 partially toward its retracted position following each fastener firing operation (i.e., as opposed to using the lifter mechanism 98 to raise the drive blade 22 from its driven position to its retracted position), the cycle time between consecutive firing operations may be reduced, allowing for more rapid placement of fasteners into a workpiece.

[0032] With reference to FIGS. 9 and 10, another gas spring fastener driver 10a for driving fasteners (e.g., nails, tacks, staples, etc.) into a workpiece is shown, with like components as the fastener driver 10 of FIGS. 1-8 being shown with like reference numerals plus the letter “a.” Rather than including only a single extensible cylinder, the fastener driver 10a includes two extensible cylinders 54a, one positioned on each side of the gas spring mechanism 30a. And, the rods 62a of the respective extensible cylinders 54a are affixed to corresponding flanges 66a on the head 46a of the drive blade 22a.

[0033] With reference to FIG. 10, the lift mechanism 98a includes two cam lobes 106a coupled for synchronous co-rotation with respective large-diameter driven gears 126a which, in turn, receive torque from the motor 102a via a transmission 200. The follower 134a protrudes from both the front and rear of the head 46a of the drive blade 22a, and is engageable by both cam lobes 106a for raising the drive blade 22a from its intermediate position (as described above) to its retracted position. Otherwise, the fastener driver 10a functions identically to the fastener driver 10 as described above.

[0034] Various features of the invention are set forth in the following claims.