EP3036069B1

EP3036069B1 - Pneumatic fastener driver

Info

Publication number: EP3036069B1
Application number: EP14838000.9A
Authority: EP
Inventors: Jin Lin Zhou; Guo Hui XIONG; Ying Xiang TAN
Original assignee: Techtronic Power Tools Technology Ltd
Current assignee: Techtronic Power Tools Technology Ltd
Priority date: 2013-08-22
Filing date: 2014-05-13
Publication date: 2020-11-11
Anticipated expiration: 2034-05-13
Also published as: CN105339137A; EP3036069A1; CN105339137B; WO2015024398A1; EP3036069A4

Description

FIELD OF THE INVENTION

The present invention relates to a pneumatic fastener driver.

BACKGROUND OF THE INVENTION

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. A hammering tool having improved usability is described in WO 2011/010634 . Said hammering tool comprises a motor, a first cylinder, and a first piston that is driven by the motor and moves back and forth inside the first cylinder, thereby generating compressed air. The hammering tool further comprises a second cylinder, a second piston that moves in the second cylinder and hammers in a fastener, and an elongated handle extending in a direction that intersects the central axis of the first cylinder. The first cylinder and the second cylinder are arranged so as to at least partially overlap in the radial direction. A fastener driving apparatus for driving fasteners into a substrate is described in US 2008/190988 . The fastener driving apparatus is a combination of a motor driven linear motion converter, a compression cylinder, an expansion cylinder, and a valve arrangement. The linear motion converter converts a rotational motion of a motor to a linear motion of a compression piston within the compression cylinder causing a gas within the compression cylinder to be compressed. The compressed gas is communicated to the expansion cylinder through the valve arrangement wherein the compressed gas expands causing an anvil coupled to an expansion piston within the expansion cylinder to move axially. The axial movement of the anvil causes a fastener to be driven into the substrate. The fastener driving apparatus is an ergonomically designed portable hand held tool providing comfort to a user.

SUMMARY OF THE INVENTION

Accordingly, in one aspect of the present invention there is provided a pneumatic fastener driver containing a cylinder, a piston, a motor, a rack, and a magnetic latch. The piston is positioned within the cylinder and moveable between a top-dead-center position and a bottom-dead-center position. The rack is coupled to the piston and operable to drive the piston to move within the cylinder. The rack is driven by the motor via a pinion. The magnetic latch emits a magnetic field that magnetically attracts the piston and is capable of holding the piston in the top-dead-center position with a magnetic force, wherein the magnetic latch is adjustable to vary the magnetic force acting on the piston for driving fasteners into a workpiece at different depths.
Preferably, the magnetic latch includes a magnet emitting the magnetic field and a ferromagnetic portion of the piston.
More preferably, the magnet is annular.
In one implantation, the magnet is positioned adjacent a top end of the cylinder.
In another implantation, the magnetic latch includes a plunger movable between a first position in which a first gap is created between the ferromagnetic portion of the piston and the magnet resulting in a first magnetic force acting on the piston, and a second position in which a second gap smaller than the first gap is created between the ferromagnetic portion of the piston and the magnet resulting in a second magnetic force acting on the piston larger than the first magnetic force.
Preferably, the magnetic latch includes an actuator operable to move the plunger between the first and second positions.
More preferably, the plunger is threadably coupled to the cylinder, and the actuator is rotatable for moving the plunger between the first and second positions.
In one variation, the piston is displaced from the top-dead-center position to the bottom-dead-center position when the actuator is in the first position and when a force of compressed air acting on the piston exceeds the first magnetic force.
Preferably, the piston is displaced from the top-dead-center position to the bottom-dead-center position when the actuator is in the second position and when a force of compressed air acting on the piston exceeds the second magnetic force.
In one variation, the piston is a first piston and the cylinder is a first cylinder, and wherein the pneumatic fastener driver further includes a second cylinder at least partially surrounding the first cylinder and in fluid communication with the first cylinder, and a second piston positioned within the second cylinder and including a bore through which the first cylinder extends.
In another variation, the pneumatic fastener driver further contains a fastener connecting the rack to the piston; a seal disposed around a shank of the fastener.
In another aspect of the present invention, a pneumatic fastener driver contains a first cylinder; a first piston positioned within the first cylinder; a second cylinder positioned within the first cylinder; a second piston positioned within the second cylinder; a motor; a rack coupled to said first piston and operable to drive said first piston to move within the first cylinder; the rack driven by the motor via a pinion; and means for positioning the second cylinder relative to the first cylinder.
Preferably, the pneumatic fastener driver further contains a cylinder head coupled to a first end of the first cylinder; and an end cap positioned within the first cylinder proximate the first end, wherein the positioning means includes an opening formed in the cylinder head to receive a stem portion of the end cap.
Preferably, the positioning means further includes a cylindrical recess formed in the end cap in which the second cylinder is at least partially received.
Preferably, the end cap includes vents for fluidly communicating the first cylinder and the second cylinder.
In one variation, the vents fluidly communicate the first cylinder and the second cylinder via the cylindrical recess.
In one implementation, the pneumatic fastener driver further contains a plunger positioned within the stem portion of the end cap, wherein the plunger includes vents corresponding to the vents of the end cap for fluidly communicating the first cylinder and the second cylinder.
Preferably, the pneumatic fastener driver a fastener connecting the rack to the piston; a seal disposed around a shank of the fastener.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
By using the magnetic latch and the length-configurable latch in the pneumatic fastener driver, the present invention enables a convenient method of adjusting the driving depth of the fastener which is driven by the fastener driver. Also, use of the rack and pinion assembly results in reduction of the overall size of the pneumatic fastener driver

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a pneumatic fastener driver in accordance with an embodiment of the invention.
FIG. 2 is an enlarged, partial cross-sectional view of the pneumatic fastener driver of FIG. 1 with an emphasis on the drive assembly.
FIG. 3 is an enlarged, partial cross-sectional view of the pneumatic fastener driver of FIG. 1 with an emphasis on the magnetic latch and cylinder part.

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.

DETAILED DESCRIPTION

With reference to Fig. 1, a pneumatic fastener driver is operable to drive fasteners (e.g., nails, tacks, staples, etc.) held within a magazine 20 into a workpiece. The pneumatic fastener driver in general includes a machine body 26, a handle portion 22, a motor housing 24, and a magazine 20 which is detachably installed to the machine body 26. Note that as illustrated in the drawing the magazine 20 when installed to the pneumatic fastener driver is align to the machine body 26 forms an inclined angle. In other words, the magazine 20 is not perpendicular to the machine body 26. Such arrangement would help reducing the overall size of the pneumatic fastener driver.
The handle portion 22 is to be used as a gripping portion for the user to hold the pneumatic fastener driver in operation. The motor housing 24, which is substantially parallel to the handle portion 22 and formed at a front end of the machine body 26, may also be used as a gripping portion for the user to grip. For example, the user may use his both hands to grip the handle portion 22 and motor housing 24 at the same time to hold the pneumatic fastener driver firmly. As shown in Fig. 1, the bottom parts of the handle portion 22 and the motor housing 24 are formed as an integral part, which helps to enhance the strength of the whole pneumatic fastener driver casing. On the handle portion 22, there is configured a user actuating trigger 28 for the user to control driving of the fastener into the workpiece. The trigger 28 is biased by a spring 30 to an inactivated position, so that the pneumatic fastener driver would operate to drive the fasteners only when the trigger 28 is pressed by the user.
With reference to Figs. 2 and 3, in the illustrated embodiment of the fastener driver a drive assembly at least partially contained in the motor housing 24 includes a motor 32, a transmission 34 that receives torque from the motor 32, a pinion 36 drivably coupled to the output of the transmission 34, and a rack 38 meshed with the pinion 36 and connected to the compress piston 40 for reciprocation therewith. The use of pinion-rack mechanism in the pneumatic fastener driver further helps reduce the overall size of the pneumatic fastener driver compared to the traditional pneumatic fastener drivers in which crank arm assembly is used for power transmission.
Preferably, the compress piston 40 further includes a rack seal (not shown) in a recess formed inside the compress piston 40. A fastener (not shown) connects the rack 38 to the compress piston 40, and the rack seal is disposed around a shank of the fastener. The rack seal 126 is preferably an O-ring or a lip seal. The rack seal is moved between the first position and the second position in response to relative movement between the rack 38 and the compress piston 40 (i.e., when the rack 38 is driven upwards or downwards by the motor 32). A leak path is at least partially defined by the recess mentioned above, an aperture communicating the recess to the outside when the seal is in the second position. The leak path is formed at least in part through a groove formed in the rack 38. In alternative embodiments, the leak path is formed at least in part through a groove formed in the compress piston 40.
The pneumatic fastener driver includes a drive blade 44 actuated by the on-board air compressor to drive the fasteners into a workpiece. The compressor includes a compressor cylinder 46 and the compression piston 40 is movable in the compressor cylinder 46 driven in a reciprocating manner by the above mentioned motor 32, transmission 34, pinion 36 and rack 38. The pneumatic fastener driver 10 also includes a drive cylinder 48 in fluid communication with the compressor cylinder 46 and a drive piston 50 slidably disposed in the drive cylinder 48. As shown in Fig. 3, the smaller drive cylinder 48 is located inside the larger compressor cylinder 46 for a cylinder-in-a-cylinder configuration, while the side wall of the drive cylinder 48 is separated from that of the compressor cylinder 46. Bumper 42 and 43 are positioned in both the top and bottom portions of the compress cylinder 46, which absorbs impact forces from both the compress piston 40 and drive piston 50. Also, in the compress piston 40 there is embedded a magnet 47. Correspondingly, a PCB board 49 is placed substantially parallel to the movement direction of the compress piston 40, and on the PCB board 49 there are Hall sensors (not shown) placed. The Hall sensors, by sensing position of the magnet 47, detect the position of the compress piston 40 in the compress cylinder 46, which facilitate control of the motor 32 by a controlling circuit of the pneumatic fastener driver.
The maximum displacement of the compress piston 40 in the compressor cylinder 46 can be controlled by adjusting length of rack 38. The maximum displacement of the compress piston 40 determines the volume of vacuum generated by the compress piston and therefore has influence on the driving depth of the fasteners in operation.
The compressor piston 40 includes a bore 52 through which the drive cylinder 48 extends. The drive piston 50 includes a body 54 and a ferromagnetic cap 56 is secured to the body 54 by a bolt 58. The drive blade 44 is attached to the main body 54 of the drive piston 50 by a fastening mechanism such as a pin (not shown) that is interference-fit to the main body 54. The drive piston 50 is movable between a top-dead-center position (Fig. 3) and a bottom-dead-center position (not shown, which is close to the pinion 36 in Fig. 2). The drive cylinder 48 includes a plurality of one-way check valves 60 formed therein to vent excess pressure in the drive cylinder 48 when the drive piston 50 reaches the bottom-dead-center position. Specifically, the check valves 60 are configured as flapper valves that equalize the pressure within the drive cylinder 48 above the drive piston 50 and the pressure within the compressor cylinder 46 below the compressor piston 40 when the valves 60 are uncovered upon the drive piston 50 reaching the bottom-dead-center position. This ensures that there is no excess pressure above the drive piston 50 that would otherwise inhibit the drive piton 50 from being retracted to the top-dead-center position as described in detail below.
Similarly, the compressor piston 40 is moveable between a top-dead-center position (not shown, but approximate the leftmost end of the compress cylinder 46 in Fig. 3) and a bottom-dead-center position (Fig. 3). An end cap 62 is positioned within the compressor cylinder 46 adjacent a top end 64 of the compressor cylinder 46, such that a stem portion 66 of the end cap 62 extends through an opening 68 formed in the cylinder head. A combination of the opening 68 in the cylinder head and the stem portion 66 of the end cap 62 provides a means to position and align the drive cylinder 48 within the compressor cylinder 46. In addition, a cylindrical recess 70 is formed in the end cap 62 to receive and position the drive cylinder 48 within the compressor cylinder 46. Accordingly, the cylindrical recess 70 in the end cap 62 can further be considered as a feature of the positioning means described above. Alternatively, a boss or any other alignment feature formed on the cylinder head of the compressor cylinder 46 could facilitate positioning and alignment of the drive cylinder 48 within the compressor cylinder 46. The end cap 62 further includes vents (not shown) to enable fluid communication between the compressor cylinder 46 and the drive cylinder 48. Likewise, the cylindrical recess 70 fluidly communicates the compressor cylinder 48 and the drive cylinder 48.
With reference to Fig. 3, the pneumatic fastener driver 10 further includes a magnetic latch capable of holding the drive piston 50 in the top-dead-center position with a magnetic force. The latch includes an annular magnet 72 positioned near the top of the drive cylinder 48. The annular magnet 72 emits a magnetic field that magnetically attracts the ferromagnetic cap 56, which is also a part of the magnetic latch. Alternatively, the magnetic latch could include a ferromagnetic portion positioned near the top of the drive cylinder 48 and a magnet secured to the drive piston 50. The magnetic latch also includes a plunger 74 movable between a first position in which a first gap (not shown) is created between the ferromagnetic cap 56 of the drive piston 50 and the magnet 72 resulting in a first magnetic force acting on the drive piston 50, and a second position in which a second gap (not shown) smaller than the first gap is created between the ferromagnetic cap 56 of the drive piston 50 and the magnet 72 resulting in a second magnetic force acting on the drive piston 50 larger than the first magnetic force. In the illustrated embodiment of the pneumatic fastener driver, an internally threaded collar 76 is affixed (e.g., via an interference fit or insert-molding process, etc.) within the stem portion 66 of the end cap 62 and the plunger 74 includes external threads engaged with the internal threads of the collar 76. Due to the pitch of the engaged threads of the plunger 74 and collar 76, rotation of the plunger 74 with respect to the threaded collar 76 causes the plunger 74 to translate (i.e., move along a central axis 78) between the first and second positions. Although the threaded collar 76 and the end cap 62 are separate components in the illustrated embodiment, the threaded collar 76 may alternatively be integrally formed as a single piece with the end cap 62.
The magnetic latch further includes an actuator 80 accessible from the top of the outer housing 26 for moving the plunger 74 between the first and second positions. Particularly, rotation of the actuator 80 about the central axis 78 translates the plunger 74 relative to the threaded collar 76, as described in detail above, moving the plunger 74 between the first and second positions. The plunger 74 includes vents (not shown) formed in the end cap 62 to place the drive cylinder 48 in fluid communication with the compressor cylinder 46.
At the beginning of a fastener driving operation of the pneumatic fastener driver illustrated in the drawings, the magnetic latch maintains the drive piston 50 in the top-dead-center position, while the compressor piston 40 is located in the bottom-dead-center position. When the user of the pneumatic fastener driver depresses the trigger 28, the compressor piston 40 is driven upward and toward the top end 94 of the compressor cylinder 46 by the motor 32, the pinion 36 and the rack 38 (FIG. 2). As the compressor piston 40 travels upward, the air in the compressor cylinder 46 and above the compressor piston 40 is compressed. Because the top end of the drive cylinder 48 is in fluid communication with the compressor cylinder 46 via the associated vents in the plunger 74 and the end cap 62, respectively, the compressed air also acts upon the drive piston 50. The magnetic latch, however, holds or maintains the drive piston 50 in the top-dead-center position shown in FIG. 3 so long as the force of the compressed air acting on the drive piston 50 is less than the magnetic force acting on the drive piston 50 to maintain it in the top-dead-center position.
As the compressor piston 40 approaches the top-dead-center position, the force of the compressed air acting on the drive piston 50 overcomes the magnetic force acting on the drive piston 50, and the drive piston 50 is accelerated downward within the drive cylinder 48 by the compressed air. As the drive piston 50 is driven downwards, the drive blade 44 impacts a fastener held in the magazine 20 and drives the fastener into a workpiece until the drive piston 50 reaches the bottom-dead-center position. Upon the drive piston 50 reaching the bottom-dead-center position, any compressed air still acting on the drive piston 50 is vented from the drive cylinder 48 through the check valves 60. Finally, to prepare for a subsequent fastener driving operation, the compressor piston 40 is driven downwards towards the bottom-dead-center position by the motor 54 and pinion-rack assembly as mentioned above. As the compressor piston 40 is driven downward, a vacuum is created within the compressor cylinder 46 and the drive cylinder 48, between the compressor piston 40 and the drive piston 50. The vacuum draws the drive piston 50 upwards in the drive cylinder 48 until the ferromagnetic cap 62 of the drive piston 50 abuts the plunger 74, after which time the magnetic latch again holds or maintains the drive piston 50 in the top-dead-center position.
The magnetic latch may be adjusted to vary the depth to which fasteners are driven into a workpiece. For example, to increase fastener driving depth, the actuator 80 is rotated in one direction to move the plunger 74 upward and toward a top end of the drive cylinder 48 to create a smaller gap 130 (FIG. 3) between the magnet 72 and the ferromagnetic cap 62, increasing the magnetic force between the magnet 72 and the ferromagnetic cap 62. With the larger magnetic force, a larger compressed air force is needed to overcome the magnetic force and to release the drive piston 50. The larger compressed air force causes the drive piston 50, and subsequent drive blade 42, to drive the fastener deeper into the workpiece. Alternatively, to reduce the driving depth of the fastener, the actuator 80 is rotated in an opposite direction to move the plunger 74 downward and away from the top end of the drive cylinder 48 to create a larger gap between the magnet 72 and ferromagnetic cap 62, decreasing the magnetic force between the magnet 72 and the ferromagnetic cap 62. The lower magnetic force is overcome by a lower compressed air force, resulting in a reduced fastener driving depth.
Various features and advantages of the invention are set forth in the following claims.

Claims

A pneumatic fastener driver (10) comprising:
a cylinder (46, 48);

a piston (40, 50) positioned within the cylinder and moveable between a top-dead-center position and a bottom-dead-center position;

a motor (32);

a rack (38) coupled to said piston and operable to drive said piston to move within the cylinder; the rack driven by the motor via a pinion (36); charaterized by a magnetic latch emitting a magnetic field that magnetically attracts the piston and is capable of holding the piston in the top-dead-center position with a magnetic force, wherein the magnetic latch is adjustable to vary the magnetic force acting on the piston for driving fasteners into a workpiece at different depths.
The pneumatic fastener driver (10) of claim 1, wherein the magnetic latch includes a magnet (72) emitting the magnetic field and a ferromagnetic portion (56) of the piston (50).
The pneumatic fastener driver (10) of claim 2, wherein the magnet (72) is annular.
The pneumatic fastener driver (10) of claim 2, wherein the magnet (72) is positioned adjacent a top end (64) of the cylinder (46).
The pneumatic fastener driver (10) of claim 2, wherein the magnetic latch includes a plunger (74) movable between a first position in which a first gap is created between the ferromagnetic portion (56) of the piston (50) and the magnet (72) resulting in a first magnetic force acting on the piston, and a second position in which a second gap smaller than the first gap is created between the ferromagnetic portion of the piston and the magnet resulting in a second magnetic force acting on the piston larger than the first magnetic force.
The pneumatic fastener driver (10) of claim 5, wherein the magnetic latch includes an actuator (80) operable to move the plunger (74) between the first and second positions.
The pneumatic fastener driver (10) of claim 6, wherein the plunger (74) is threadably coupled to the cylinder (46), and wherein the actuator (80) is rotatable for moving the plunger between the first and second positions.
The pneumatic fastener driver (10) of claim 6, wherein the piston (50) is displaced from the top-dead-center position to the bottom-dead-center position when the actuator (80) is in the first position and when a force of compressed air acting on the piston exceeds the first magnetic force.
The pneumatic fastener driver (10) of claim 6, wherein the piston (50) is displaced from the top-dead-center position to the bottom-dead-center position when the actuator (80) is in the second position and when a force of compressed air acting on the piston exceeds the second magnetic force.
The pneumatic fastener driver (10) of claim 1,
wherein the piston (50) is a first piston and the cylinder (48) is a first cylinder, and wherein the pneumatic fastener driver further includes a second cylinder (46) at least partially surrounding the first cylinder and in fluid communication with the first cylinder, and a second piston (40) positioned within the second cylinder and including a bore (52) through which the first cylinder extends;
or
further comprising a fastener connecting the rack (38) to the piston (40); a seal disposed around a shank of the fastener.
A pneumatic fastener driver (10) comprising:
a first cylinder (46);

a first piston (40) positioned within the first cylinder;

a second cylinder (48) positioned within the first cylinder;

a second piston (50) positioned within the second cylinder;

a motor (32);

a rack (38) coupled to said first piston and operable to drive said first piston to move within the first cylinder; the rack driven by the motor via a pinion (36); characterized by means for positioning the second piston relative to the first piston;

wherein the means for positioning the second piston relative to the first piston comprises a magnetic latch emitting a magnetic field that magnetically attracts the second piston and is capable of holding the second piston in a top-dead-centre position with a magnetic force, wherein the magnetic latch is adjustable to vary the magnetic force acting on the second piston for driving fasteners into a workpiece at different depths.
The pneumatic fastener driver (10) of claim 11,
further comprising a cylinder head coupled to a first end of the first cylinder (46); and an end cap (62) positioned within the first cylinder (46) proximate the first end (64), wherein the positioning means includes an opening (68) formed in the cylinder head to receive a stem portion (66) of the end cap.
or
further comprising a fastener connecting the rack (38) to the piston (40); a seal disposed around a shank of the fastener.
The pneumatic fastener driver of (10) claim 12, wherein the positioning means further includes a cylindrical recess (70) formed in the end cap (62) in which the second cylinder (48) is at least partially received.
The pneumatic fastener driver (10) of claim 13, wherein the end cap (62) includes vents for fluidly communicating the first cylinder (46) and the second cylinder (48).
The pneumatic fastener driver (10) of claim 14, wherein the vents fluidly communicate the first cylinder (46) and the second cylinder (48) via the cylindrical recess (70); and, optionally, further comprising a plunger (74) positioned within the stem portion (66) of the end cap (62), wherein the plunger includes vents corresponding to the vents of the end cap for fluidly communicating the first cylinder and the second cylinder.