Patent Application
20220347825
In certain situations however, there is an increased risk of injury with the contact triggering method. If the user does not only hold down the manually-actuated trigger for example when they wish to place the compressed air nail gun on one and the same workpiece at a distance of a few centimeters from the most recently driven-in fastening means, but rather also when they change to another workpiece, arranged further away, a drive-in process may be triggered by unintended contact of an object or a body part with the contact sensor. For example, accidents may occur if a user (when not observing important safety requirements) climbs a ladder with the compressed air nail gun, with the trigger held down in the process, and accidentally brushes their leg with the contact sensor.
Some known compressed air nail guns seek to reduce this risk associated with the contact triggering operation by contact triggering being possible only for a brief time period after actuating the trigger or after a drive-in process. If this time period lapses, the trigger must first be released again. An example of this is known from the publication EP 2 767 365 B1. The compressed air nail gun described therein has a trigger and a contact sensor to each of which a control valve is assigned. Additionally, the known device has a safety control chamber, whose pressure acts on a locking piston. In a certain position of the locking piston, the triggering of a drive-in process is prevented. The safety control chamber is aerated via the control valve, assigned to the trigger, and a throttle. As a result, after actuating the trigger, contact triggering is possible only until the pressure in the safety control chamber has exceeded a specified pressure threshold. After this, the compressed air nail gun is locked until the trigger is released and the pressure in the safety control chamber has once again decreased below the pressure threshold.
A similar functionality is offered by the compressed air nail gun known from U.S. Pat. No. 3,964,659 which can also be used in a single triggering operation and in a contact triggering operation and in which a trigger and a contact sensor are mechanically coupled via a rocker. The rocker acts on a control valve in order to trigger a drive-in process by deaerating a main control line. If only the trigger and not the contact sensor is actuated, a control pin of the control valve is moved only over a part of its adjustment path. This half actuation of the control valve leads to a slow aeration of a control chamber via a small adjustable aeration opening. The pressure prevailing in the control chamber acts on a valve sleeve which surrounds the control valve and moves this valve sleeve ultimately into a locked position in which a full actuation of the valve pin can no longer deaerate the main control line such that contact triggering is not possible.
A further improvement in safety can be achieved if a first drive-in process must always be carried out by individual triggering. In this case, the device must first be placed on the workpiece for the first drive-in process, whereby the contact sensor is actuated. A subsequent actuation of the trigger then triggers the first drive-in process. After that, further drive-in processes can take place within a short time period by contact triggering, i.e. by repeatedly lifting and placing down the device on the workpiece with continuously actuated trigger. This functionality is present in the case of the compressed air nail gun described in the publication DE 10 2013 106 657 A1. To this end, a trigger and a contact sensor are mechanically coupled via a rocker which acts on a control valve in order to trigger a drive-in process. With each drive-in process, a pressure is built up in a relatively large-volume control chamber, which surrounds a working cylinder in a ring shape, said pressure acting on a mechanical actuating member. The control chamber is slowly deaerated via a deaeration opening in a wall of the working cylinder. The actuating member reaches a locked position depending on the pressure in the control chamber, whereby a mechanical action of the contact sensor on the rocker is prevented when the trigger is actuated and contact triggering is made impossible.
From document WO 2019/038124 A1, a compressed air nail gun is known in which the described functionality is achieved by pneumatic means. For this purpose, a control chamber is aerated via the control valve when a control valve is actuated. A delay time, after which the compressed air nail gun returns from the contact triggering operation to the individual triggering operation, results from slow deaeration of the control chamber by a throttle. In one exemplary embodiment, the control chamber merges into a first, smaller storage chamber, which is connected to a second, larger storage chamber via a first throttle. When a drive-in process is triggered, the smaller storage chamber is aerated via a control valve. In addition, the larger storage chamber is aerated from a return chamber. The slow deaeration takes place via a second throttle, which connects the second storage chamber to external air. In this way, a larger quantity of air can be used to adjust the delay time than could be provided by the control valve alone in the time available. This should enable the use of an easy-to-produce, less failure-prone throttle with a relatively large opening cross-section, in particular in the form of a small borehole with a diameter in the range of 0.1 mm to 1 mm.
Based on this, the object of the invention is to provide a compressed air nail gun with a compact design and a simple, robust and reliable safety mechanism.
This object is achieved by the compressed air nail gun with the features as described herein. Advantageous embodiments are indicated in the dependent claims.
The compressed air nail gun has
The compressed air nail gun is used for driving in fastening means, such as nails, pins or staples. To this end, the compressed air nail gun can have a magazine for the fastening means from each of which one fastening means is supplied to a receiver of an outlet tool of the compressed air nail gun. When a drive-in process is triggered, compressed air is applied to the working piston of the compressed air nail gun. The working piston drives a driving ram which is connected to the working piston. The driving ram impinges upon a rear end of the fastening means in the receiver of the outlet tool and drives the fastening means into the workpiece.
The contact sensor can be a mechanical structural element which protrudes over the front end of the outlet tool and is held in this position by a spring until the compressed air nail gun is placed on a workpiece. Then, the contact sensor is moved counter to the direction of the spring force and counter to the drive-in direction until an outlet tool of the compressed air nail gun lies on, or nearly on, the workpiece. As a further actuation element, the compressed air nail gun has a trigger, for example in the form of a trigger lever that can be actuated with a finger.
The safety device is responsible for preventing a drive-in process being triggered in certain, potentially dangerous situations. For this purpose, it automatically takes a safety measure which ensures that no drive-in process is triggered despite a common actuation of the contact sensor and trigger. For example, the safety measure can be to disconnect the compressed air nail gun from a pressure supply line and deaerate it completely. However, less intrusive safety measures are also possible, in particular those in which the compressed air nail gun is brought back into a ready-to-operate state by simply briefly releasing the trigger. Details on this will be explained later.
As in the case of the prior art discussed at the beginning, in particular in document WO2019/038124 A1, the safety device automatically takes the safety measure after expiry of a delay time. The delay time starts to run from a certain event, for example from an actuation of the trigger or a previous drive-in process. At this point in time, the pressure in the control volume may have a certain initial value, for example, operating pressure or ambient pressure. From this point on, the control volume is aerated or deaerated via the throttle until the pressure in the control volume exceeds or undercuts a specified pressure threshold. The delay time ends at this point. The duration of the delay time is therefore determined by the volume of the control chamber and the opening cross-section of the throttle.
In the invention, the control volume has a volume in the range from 0.5 ml to 20 ml, in particular in the range from 0.5 ml to 10 ml, in the range from 0.5 ml to 5 ml, in the range from 0.5 ml to 2 ml or in the range from 1 ml to 1.5 ml. The throttle is a borehole with a diameter in the range from 30 μm to 200 μm, in particular in the range from 30 μm to 95 μm, in the range from 40 μm to 80 μm or in the range from 60 μm to 80 μm. The borehole can in particular have a substantially circular cross-section. Thus, a relatively small volume is combined with a small opening cross-section in order to achieve a reasonable delay time. Unlike what is known in the prior art in connection with small control volumes, a simple, small borehole is used instead of a throttle whose opening cross-section is formed by an adjustable annular gap. These measures result in a particularly compact, structurally simple design.
In addition, the inventors have recognised that an annular gap with a sufficiently small opening cross-section has a very small gap width, which can for example be in the range of a few um or even less, and that such an annular gap easily clogs over time during operation of the compressed air nail gun. This is detrimental to the safety of the device, as the delay time may be extended unnoticed under certain circumstances until the safety device may no longer even respond. It is assumed that the clogging of the annular gap is caused by the smallest particles, whose penetration into the compressed air nail gun can hardly be prevented, simply because such particles, such as in particular fine dust, can already be contained at a certain concentration in the compressed air used to operate the devices. Although the borehole used in the invention has an opening cross-section comparable to the annular gap, the diameter of the borehole is significantly larger than the width of the annular gap. The inventors have determined that the safety device is significantly less sensitive to soiling when using a borehole instead of a throttle with an annular gap and attribute this to the different dimensions of the respective openings mentioned.
Overall, the invention thus provides a structurally simple, compact and particularly reliable safety device.
In one configuration, the borehole is produced by laser drilling. In principle, the borehole can be produced using any method, in particular a machining method with a conventional drill or milling cutter.
However, producing very small boreholes with machining processes is difficult and requires expensive and sensitive special tools that wear quickly. Laser drilling is an alternative in which the material, in which the borehole is made, is not machined, but evaporated and/or liquefied by means of a laser. Unlike machining processes, it is not possible to drill exactly cylindrical boreholes with laser drilling under certain circumstances. However, this is not important for the invention. More important is the reproducibility of the borehole dimensions, which can easily be achieved with the required quality using laser drilling. A particular advantage of laser drilling in comparison with the machining methods is the largely burr-free contour of the borehole edges, which can be important in the invention with a view to a possible “sticking” of dirt particles.
In one configuration, the borehole has a length in the range of 30 μm to 1 mm. This means that the component in which the borehole is inserted has a corresponding thickness directly adjacent to the borehole. For this purpose, the material thickness of the component in the area of the borehole can be reduced accordingly before the borehole is produced. The length of the borehole, as well as its diameter, influences the compressed air flow through the borehole. For the low compressed air flow desired at a low control volume in order to achieve a reasonable delay time, a relatively long borehole may therefore be sensible. Tests have shown that the length of the borehole in the mentioned range is in many cases suitable in practice. It may be difficult to produce a particularly long borehole under certain circumstances. Therefore, a length in the range of 30 μm to 200 μm, in particular in the range of 40 μm to 100 μm, is particularly suitable. The borehole can have the same diameter over its entire length, i.e. be exactly cylindrical. However, this is not necessary for the invention; production-related deviations such as for example a certain conicity of the borehole, which can occur during laser drilling, are generally unproblematic. If the borehole deviates from an exactly cylindrical shape, an average diameter over the length of the borehole or a minimum diameter of the borehole can be used as the diameter of the borehole.
In one configuration, the compressed air nail gun has a first control valve, which is actuated with each actuation of the trigger, with the control volume being aerated or deaerated via the first control valve. The first control valve is assigned to the trigger and is therefore sometimes referred to as the triggering valve. For example, the first control valve can have a valve pin, which is moved directly from an actuating surface of the trigger lever when the trigger is actuated. As a result of this actuation, the first control valve establishes a connection via which the control volume is aerated or deaerated, for example a connection between the control volume and a space permanently under operating pressure or between the control volume and external air. In this configuration, the explained delay time can begin with the actuation of the trigger.
In one configuration, the compressed air nail gun has a second control valve, which is actuated with each actuation of the contact sensor or with each common actuation of trigger and contact sensor, with a main control line being aerated and/or deaerated via the second control valve. The second control valve is assigned to the contact sensor and is therefore sometimes also referred to as the contact sensor valve. Whether it is actuated each time the contact sensor is actuated or only when the trigger is actuated at the same time depends on the design of the compressed air nail gun. Both variants are explained in connection with the exemplary embodiments. In any case, the effect of the actuation of the second control valve is that a main control line is aerated and/or deaerated. To this end, the second control valve can in particular establish a connection between the main control line and a space permanently under operating pressure or between the main control line and external air. A drive-in process can be initiated by aerating or deaerating the main control line. For this purpose, for example, a design is known having a main valve and a pilot valve, which is actuated via the main control line. However, other designs with or without pilot valve are also conceivable. For the configuration of the invention, it is only important that the drive-in process can be triggered by aerating or deaerating the main control line.
In one configuration, the control volume includes an annular volume, which surrounds a control valve. In principle, the control volume can have any geometry. However, with many designs of compressed air nail guns, the available installation space is limited, so that even the relatively small control volume in case of the invention cannot easily be accommodated. The use of an annular volume around a control valve takes this situation into account. The control valve can in particular be the explained first control valve or the explained second control valve.
In one configuration, the compressed air nail gun comprises a housing which has a recess in which a control valve arrangement is arranged, with the control volume being arranged in full or in large part in the recess. The housing can for example enclose the working cylinder of the compressed air nail gun and/or have a handle section. The recess can for example be arranged inside the handle section. The control valve arrangement can in particular comprise the explained first control valve and/or the explained second control valve. The control valve arrangement can be sealed with respect to the surrounding housing. The control volume can be located between the control valve arrangement and the housing. In this configuration, a particularly compact and structurally simple design is obtained.
In one configuration, the borehole is arranged in a replaceable component of the compressed air nail gun. The replaceable component is in particular a component different from the housing of the compressed air nail gun, for example an element of a control valve arrangement or a compressed air line. On the one hand, this configuration enables simplified maintenance or repair of the borehole, for example in order to be able to thoroughly remove dirt or corrosion. On the other hand, by simply replacing the replaceable component, the delay time can be adapted to the respective requirements by using replaceable components with different borehole diameters and/or lengths.
For the latter purpose, in a further configuration, it is conceived that at least one second copy of the replaceable component is present, which differs from the replaceable component in diameter and/or length of the borehole. In particular, the compressed air nail gun with the replaceable component and the at least one, second copy of the replaceable component can be offered in a set.
In one configuration, the replaceable component is a valve sleeve. In particular, this can be a valve sleeve of the first control valve, whereby a particularly simple and compact design is achieved for aerating or deaerating the control volume through the borehole and controlled by the first control valve.
In one configuration, the safety measure is that the compressed air nail gun is moved to a locked state in which no drive-in process can be triggered. For example, the compressed air nail gun can have a locking piston, which mechanically intervenes in an operation required to trigger a drive-in process, for example by preventing an actuating member of a pilot valve from moving. Alternatively, the locked state can be established by shutting off the compressed air nail gun from a compressed air supply by means of a shut-off valve and/or completely deaerating it. It is also possible to establish the locked state by opening or shutting off a control line, which must be aerated or deaerated in order to trigger a drive-in process, by means of a shut-off valve. This control line can in particular be the main control line already mentioned.
In one configuration, the compressed air nail gun can be operated in a contact triggering operation and in a single triggering operation, and the safety measure is that the compressed air nail gun is moved from the contact triggering operation to the single triggering operation. As explained in the introduction, this measure can also improve the operational safety of the compressed air nail gun. After the compressed air nail gun has been set to the single triggering operation, contact triggering is not possible. Instead, single triggering must first be carried out, which is generally only possible again once the trigger has been released beforehand.
In one configuration, the compressed air nail gun has a locking sleeve which is movable between a locked position and an open position, with the locking sleeve shutting off a connection between a main control line and a control valve in the locked position and opening it in the open position. In this configuration, the safety measure can essentially consist of the locking sleeve being moved into the locked position. The locking sleeve can be integrated into a control valve arrangement, which comprises the explained first control valve and/or the explained second control valve. In particular, the locking sleeve can receive the explained second control valve inside it.
In one configuration, the pressure in the control volume is applied to the locking sleeve. In this way, the position of the locking sleeve is directly influenced by the pressure prevailing in the control volume. The force exerted by this pressure can in particular be combined with another pneumatically generated counterforce and/or the force of a spring.
The invention will be explained in more detail below with reference to two exemplary embodiments represented in the figures. In the drawings is shown:
The compressed air nail gun from
All the elements of
The elements represented in
The trigger 26 is pivotably mounted on the housing 30 about an axis 36 fixed to the housing. At its rear end, it has an actuating surface 38 by means of which a valve pin 40 of the first control valve 22 is movable. The rear end of the contact sensor 28 interacts with a contact sensor lever 42 arranged partially inside a recess of the trigger 26. At the rear end, the contact sensor lever 42 is pivotably mounted on the housing 30 about an axis 44 fixed to the housing. The front end of the contact sensor lever 42 is entrained by the rear end of the contact sensor 28 when the contact sensor 28 moves upwards relative to the housing 30 when the compressed air nail gun is placed on a workpiece. As a result, an actuating surface 46 of the contact sensor lever 42 moves a valve pin 48 of the second control valve 24 upwards.
The first control valve 22 comprises a lower valve sleeve 50 and an upper valve sleeve 52. A small borehole 54 is arranged in the transverse direction in the lower valve sleeve 50. This borehole 54 has a diameter of about 70 μm and a length of about 200 μm. Due to these very small dimensions, the borehole 54 in
In the position of the first control valve 22 shown, the lower O-ring 60 is not sealed on the valve pin 40, so that the obliquely arranged borehole 64 and a space 66 connected to it above a locking sleeve 68, which surrounds the second control valve 24, are also deaerated via the transverse borehole 62 in the upper valve sleeve 52.
The locking sleeve 68 is in the indicated initial state in an upper end position in which it is held by the force of a spring 70. This upper end position is an open position. A further force on the locking sleeve 68 is exerted by the pressure in a control volume 72, which surrounds the second control valve 24 in a ring shape. In the indicated initial state, this force is zero because the control volume 72 has not yet been supplied with compressed air and is connected to external air via the borehole 54. In the example represented, the control volume 72 has a volume in the range between 1 ml and 1.5 ml.
As long as the valve pin 48 of the second control valve 24 is in its unactuated position, the lower O-ring 74 is not sealed on the valve pin 48. The upper O-ring 76 is also not sealed on the valve sleeve 78 of the second control valve 24. Therefore, the main control line 20 is connected to external air via a transverse borehole 80 in the locking sleeve 68, running past the upper O-ring 76, via a transverse borehole 82, an annular gap 84 between valve pin 48 and valve sleeve 78 and running past the O-ring 74.
If, starting from the state shown in
If, in the next step, the trigger 26 is also actuated, as shown in
If the compressed air nail gun is then removed from the workpiece, the contact sensor 28 moves back downwards so that the valve pin 48 of the second control valve 24 also returns to its initial position, as shown in
By re-actuating the contact sensor 28, starting from the state of
However, if the contact sensor 28 remains unactuated for a certain time when the trigger 26 is actuated, the pressure in the control volume 72 falls below a specified pressure threshold. As a result, the balance of the three forces acting on the locking sleeve 68 changes and the locking sleeve 68 enters into its lower end position shown in
Furthermore, the space designated by 96 in
A second exemplary embodiment is explained with reference to
There is a difference with the contact sensor lever 42, whose rear end is not fixed to the housing, but is hinged to a rear end of the trigger 26. As a result, the valve pin 48 of the second control valve 24 is not actuated with each actuation of the contact sensor 28, but only when trigger 26 and contact sensor 28 are actuated together. In addition, the space 66 above the locking sleeve 68 is not aerated via the first control valve 22, but is continuously connected to the housing interior 32 via a borehole 100.
The aforementioned changes with respect to the first exemplary embodiment allow a particularly simple configuration of the first control valve 22. This control valve comprises a lower valve sleeve 50 in which the borehole 54 is arranged, as explained in more detail in the first exemplary embodiment. In contrast to the first exemplary embodiment, the first control valve 22 exclusively fulfils the object of optionally aerating or deaerating the control volume 72 via the borehole 54. For this purpose, the first control valve 22, in its unactuated position indicated in
If the contact sensor 28 is actuated before expiry of the delay time with the trigger 26 still actuated, the valve pin 48 of the second control valve 24 is moved upwards, as represented in
After lifting the compressed air nail gun from a workpiece, the valve pin 48 of the second control valve 24 returns to its unactuated position and the control volume 72 is slowly deaerated via the borehole 54. Provided the pressure threshold in the control volume 72 is not undercut, the locking sleeve 68 remains in its open position so that the situation corresponds to that of
However, if the trigger 26 remains actuated without further triggering occurring within the delay time, the locking sleeve 68 is moved into its locked position shown in
In both exemplary embodiments, the housing 30 has two recesses which receive the first control valve 22 and the second control valve 24. The control volume 72 is located within the recess, which receives the second control valve 24.
10 Working piston
12 Driving ram
14 Working cylinder
16 Main valve
18 Pilot Valve
20 Main control line
22 First control valve
24 Second control valve
26 Trigger
38 Contact sensor
30 Housing
32 Housing interior
34 Handle section
36 Axis
38 Actuating surface
40 Valve pin of the first control valve
42 Trigger lever
44 Axis
46 Actuating surface
48 Valve pin of the second control valve
50 Lower valve sleeve
52 Upper valve sleeve
54 Borehole
56 Space inside the lower valve sleeve
58 Annular gap
60 Lower O-ring
62 Transverse borehole
64 Borehole
66 Space
68 Locking sleeve
70 Spring
72 Control volume
74 Lower O-ring
76 Upper O-ring
78 Valve sleeve
80 Transverse borehole
82 Transverse borehole
84 Annular gap
86 Spring
88 Upper O-ring
90 Upper O-ring
92 Middle O-ring (non-return valve)
94 O-ring
96 Space
98 Middle O-ring
100 Borehole
102 Upper O-ring
104 Lower end
106 Transverse borehole
108 Borehole
| Number | Date | Country | Kind |
|---|---|---|---|
| 19183856.4 | Jul 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/068652 | 7/2/2020 | WO |
