CROSS REFERENCE TO RELATED INVENTION

This application is a national stage application pursuant to 35 U.S.C. § 371 of International Application No. PCT/EP2018/076332, filed on Sep. 27, 2018, which claims priority to, and benefit of, European Patent Application No. 17 199 525.1, filed Nov. 1, 2017, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The invention relates to a compressed air nailer that has a trigger, a placing sensor and a trigger valve with a valve pin and valve sleeve. When the valve pin is displaced relative to the valve sleeve into an actuated position, a control line is aerated or deaerated in order to trigger a driving process. The valve pin is actuated by a switching surface which is coupled to the trigger and/or to the placing sensor.

If such a compressed air nailer is placed onto a workpiece, the placing sensor is displaced against the force of the spring until an outlet tool lies on, or nearly on, the workpiece. Only when the placing sensor has been actuated in this manner is a driving process able to be triggered. As a result, relative to devices without a placing sensor, compressed air nailers provide considerably improved safety from unintentional triggering.

Some compressed air nailers of the described kind can be used in two different operating modes: With so-called single triggering, the compressed air nailer is first placed onto a workpiece which actuates the placing sensor. Subsequently, the trigger is actuated manually and, as a result, an individual driving process is triggered. With so-called contact triggering, also denoted as “touching,” the user already holds the trigger pressed down while placing the compressed air nailer onto the workpiece. When the workpiece is touched, the placing sensor is actuated and thereby triggers a driving process. The compressed air nailer may be placed repeatedly in rapid succession which permits a very rapid operation, in particular when for sufficient fastening a plurality of fastening means have to be driven in, only low requirements being set for the positional accuracy thereof.

In specific situations, however, an increased risk of injury arises from the contact triggering method. If the user holds the manually actuated trigger pressed down, for example, not only when he wishes to position the compressed air nailer onto one and the same workpiece at a spacing of a few centimeters from the previously driven-in fastening means, but also when he changes to a different workpiece arranged at a distance therefrom, a driving process may be triggered by an unintentional contact of an object or body part with the placing sensor. For example, it may lead to accidents when a user (by ignoring important safety rules) climbs on a ladder with the compressed air nailer, holds the trigger pressed down and unintentionally touches the placing sensor with his leg.

Some known compressed air nailers attempt to reduce this risk associated with the contact triggering mode by contact triggering only being possible for a short time period after actuating the trigger or respectively, after a driving process. If the time period has elapsed, the trigger first has to be released again. An example thereof has been disclosed in the publication EP 2 767 365 B1. The compressed air nailer disclosed therein has a trigger and a placing sensor, in each case a control valve being assigned thereto. Moreover, the known device has a safety control chamber, the pressure thereof acting on a locking piston. In a specific position of the locking piston, the triggering of a driving 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 only possible until the pressure in the safety control chamber has exceeded a predetermined pressure threshold. Subsequently, the compressed air nailer is locked until the trigger is released and the pressure in the safety control chamber has dropped again below the pressure threshold.

A similar functionality is provided by the compressed air nailer which has been disclosed in U.S. Pat. No. 3,964,659 which may also be used in individual triggering mode and in contact triggering mode and in which a trigger and a placing sensor are coupled together mechanically via a rocker. The rocker acts on a control valve in order to trigger a driving process by deaerating a main control line. If merely the trigger is actuated but not the placing sensor, a control pin of the control valve is only displaced over part of its displacement path. This semi-actuation of the control valve leads to a slow aeration of a control chamber via a small aeration opening. The pressure prevailing in the control chamber acts on a valve sleeve which surrounds the control valve and finally displaces this valve sleeve into a locked position in which a complete actuation of the valve pin is no longer able to deaerate the main control line, so that contact triggering is not possible.

With some known units, initial triggering is only possible in single triggering operation. For the initial driving process, these units must also first be placed onto the workpiece which actuates the placing sensor. A subsequent actuation of the trigger then triggers the first driving process. Subsequently, within a short time period further driving processes may take place by contact triggering, i.e. by repeatedly lifting and placing the device onto the workpiece with the trigger continually actuated. This functionality is disclosed in the compressed air nailer described in the publication DE 10 2013 106 657 A1. To this end, a trigger and a placing sensor are mechanically coupled via a rocker which acts on a control valve in order to trigger a driving process. With each driving process a pressure is built in a control chamber which acts on a mechanical actuating member. The control chamber is slowly deaerated via a deaeration opening. The actuating member reaches a locked position depending on the pressure in the control chamber, whereby a mechanical action of the placing sensor on the rocker is prevented when the trigger is actuated and contact triggering becomes impossible. In an exemplary embodiment shown in one of the cited documents, the mechanical actuating member is a valve sleeve guided in an outer sleeve in which a valve pin of a trigger valve is guided. In the locked position, the valve sleeve holds the valve pin and, along with it, the rocker lying against the valve pin in a position in which the rocker is missed by the placing sensor. Then further triggering is only possible after the trigger is released and the unit has been removed from the workpiece.

Proceeding therefrom, it is the object of the invention to provide a compressed air nailer with an effective, robust and reliable safety mechanism.

BRIEF SUMMARY OF THE INVENTION

An embodiment of a compressed air nailer comprises a working piston which is connected to a driving tappet for driving in a fastening means and which is subjected to compressed air when a driving process is triggered. The compressed air nailer further comprises a trigger valve that has a valve sleeve and a valve pin guided in the valve sleeve. A control line is aerated or deaerated by the trigger valve to trigger a driving process when the valve pin is displaced relative to the valve sleeve into an actuated position. A trigger, a placing sensor as well as a switching surface which is coupled to the trigger and/or to the placing sensor for actuating the valve pin is further provided. An outer sleeve in which the valve sleeve is guided, wherein the valve sleeve can be displaced relative to the outer sleeve in accordance with a pressure in a safety control chamber between a triggering position and a locked position. The switching surface is coupled to the trigger and/or to the placing sensor such that it is always located in a permanently specified switching position or switching surface position relative to the outer sleeve when both the trigger as well as the placing sensor are actuated. The switching surface is arranged in the switching position such that it displaces the valve pin into the actuated position when the valve sleeve is located in the triggering position, and such that it does not displace the valve pin into the actuated position when the valve sleeve is located in the locked position.

The compressed air nailer is used for driving in fastening means, such as nails, tacks or staples. To this end, the compressed air nailer may have a magazine for the fastening means, in each case a fastening means being supplied therefrom to a receiver of an outlet tool of the compressed air nailer.

Both the driving as well as the controlling of the compressed air nailer can be entirely pneumatic; a supply with electrical energy is therefore unnecessary. “Deaerating” always means that a connection is established to a depressurized space, in particular to external air. “Aerating” always means that a connection is established to a space that conducts compressed air.

The trigger can for example be realized in the form of a rocker switch or sliding switch. The placing sensor can be a mechanical component which protrudes over the front end of the outlet tool and is held in this position by a spring until the compressed air nailer is placed onto a workpiece. Then the placing sensor is displaced opposite the direction of the spring force and opposite the driving direction.

When triggering a driving process, a working piston of the compressed air nailer is subjected to compressed air. In this case, the working piston drives a driving tappet which is connected to the working piston. The driving tappet strikes a rear end of the fastening means in the receiver of the outlet tool and drives the fastening means into the workpiece.

In order to trigger a driving process, a control line must be aerated or deaerated. This is accomplished by a trigger valve that is actuated by displacing a valve pin relative to a valve sleeve. For its part, the valve sleeve is guided in an outer sleeve (generally arranged in a fixed position relative to a housing of the compressed air nailer) so that it can be displaced between a triggering position and a locked position. The position in which the valve sleeve is located relative to the outer sleeve depends on a pressure in a safety control chamber.

The safety control chamber thus offers the possibility of realizing a time-controlled behavior of the compressed air nailer. For example, the pressure in the safety control chamber can be controlled such that a given pressure threshold is exceeded or undershot after the expiration of a given time period that has passed since the last driving process and/or since the last actuation of the trigger.

In an embodiment, the valve pin is actuated by means of a switching surface which is coupled to the trigger and/or to the placing sensor. Different than with some compressed air nailers explained as an introduction to the prior art, this coupling does not require a complicated, possibly failure-prone mechanism, but is rather designed such that the switching surface is always located in a permanently specified switching position relative to the outer sleeve when both the trigger as well as the placing sensor are actuated. In particular, an actuation sequence of the trigger and placing sensor is irrelevant.

Whether or not a driving process is triggered accordingly does not depend on the enabling of the coupling between the trigger and placing sensor, but rather substantially only on the position of the valve sleeve relative to the outer sleeve. The switching surface is always located in the switched position when the trigger and placing sensor are jointly actuated. If the valve sleeve is then located in the triggering position, the switching surface displaces the valve pin into the actuated position. If the valve sleeve is contrastingly located in the locked position, the switching surface does not displace the valve pin into the actuated position. Overall, the compressed air nailer is thus distinguished by a particularly simple and robust design.

In one embodiment, the compressed air nailer has a safety control valve which is controlled by the trigger and controls aeration or deaeration of the safety control chamber. The pressure characteristic of the safety control chamber therefore directly depends on the actuation of the trigger.

In one embodiment, a connection between the safety control chamber and an aerated housing interior is blocked by the safety control valve when the trigger is actuated. In this case, the safety control chamber is permanently and indirectly aerated by the safety control valve when the trigger is not actuated. This aeration ends upon an actuation of the trigger.

In one embodiment, the safety control chamber is connected via a throttle to external air. When the safety control chamber is aerated, this leads to a continuous, slight air stream which in certain circumstances is associated with an audible noise. This operating noise can indicate to the user the operational readiness of the compressed air nailer. Once an inflow into the safety control chamber ends, in particular after an actuation of the safety control valve by the trigger, the pressure in the safety control chamber slowly decreases so that the valve sleeve enters the locked position and prevents further triggering when a pressure threshold in the safety control chamber is undershot. In certain circumstances, a user can discern by the decreasing operating noise that he must first again release the trigger before another driving process.

In one embodiment, the switching surface is formed on a rocker that has a fixed end and a free end, wherein the fixed end is rotatably mounted on the trigger and the free end is entrained by the placing sensor upon an actuation of the placing sensor. This embodiment is a proven way of coupling the switching surface to the trigger and the placing sensor. Independent of the actuation sequence, the switching surface is always brought into the same switching position when the trigger and placing sensor are actuated.

In one embodiment, the switching surface is formed on the placing sensor and has a fixed position relative to the placing sensor. In this version, the switching surface is only coupled to the placing sensor and not to the trigger. If the valve sleeve is located in the triggering position, the trigger valve is accordingly controlled by each actuation of the placing sensor. If the trigger is also located in an actuated position, a driving process is triggered.

In one embodiment, the safety control valve and the trigger valve are series-connected. This means that the safety control valve and the trigger valve must be simultaneously actuated for the desired aeration or deaeration of the control line. For example, an output of the trigger valve can be indirectly or directly connected to the control line, whereas an input of the trigger valve is connected to an output of the safety control valve. An input of the safety control valve can be connected to an aerated housing interior. In this case, there can be a fixed assignment such that the placing sensor acts directly on the trigger valve and the trigger acts directly on the safety control valve. A mechanical coupling of the trigger and placing sensor is unnecessary.

In one embodiment, the safety control chamber is aerated or deaerated by the trigger valve and a non-return valve when the valve pin is displaced relative to the valve sleeve into the actuated position. By means of this measure, a driving process “resets” the pressure in the safety control chamber at the same time as a driving process is triggered. Accordingly with each driving process, a defined initial situation is established with regard to the pressure in the safety control chamber. In particular, a given time window for the triggering of additional driving processes can be opened from this point in time on when the trigger is continuously actuated.

In one embodiment, the non-return valve is integrated into the valve sleeve. For example, the non-return valve can have an O-ring which is held in a peripheral groove in the valve sleeve and seals a radial bore in the valve sleeve arranged in the groove. A particularly compact design is achieved by integrating the non-return valve into the valve sleeve.

In one embodiment, the safety control chamber has an annular space that is delimited by two seals inserted between the outer sleeve and the valve sleeve which are spaced from each other in the axial direction and radial direction. This measure as well promotes a particularly compact design. Another advantage is that the volume of the safety control chamber remains uninfluenced by an actuation of the valve pin.

In one embodiment, there is a continuously aerated counterpressure chamber, wherein the pressure in the counterpressure chamber exerts a counterforce on the valve sleeve which is directed in the direction opposite the force exerted on the valve sleeve by the pressure in the safety control chamber. Alternatively and/or in addition, a spring can be used to exert a counterforce on the valve sleeve. The use of a continuously aerated counterpressure chamber is particularly advantageous because the force exerted by the pressure in the safety control chamber and the counterforce exerted by the pressure in the counterpressure chamber equally depend on the operating pressure of the compressed air nailer. This leads to a functioning of the safety mechanism that is largely independent of pressure fluctuations.

In one embodiment, the counterpressure chamber has an annular space that is delimited by two seals adjacent to the valve sleeve which are spaced from each other in the axial direction and radial direction. This also contributes to a particularly compact design. In addition, with this annular counterpressure chamber design, the valve pin can be easily guided to the outside through a middle opening in the counterpressure chamber.

