Patent ID: 12240088

DESCRIPTION OF THE INVENTION

The compressed air nail gun fromFIG.1comprises a working piston10, which is connected to a driving ram12. The working piston10is displaceably mounted in a working cylinder14. If compressed air is applied above the working piston10, a fastening means, not represented, can be driven into a workpiece with the driving ram12. A main valve16is located above the working cylinder14, which is responsible for supplying the working cylinder14with compressed air from a compressed air reservoir, not represented, inside the compressed air nail gun or by a compressed air connection. The main valve16is actuated by a pilot valve18. In turn, the pilot valve18is actuated by a main control line20. As soon as the main control line20is aerated, the pilot valve18, and subsequently the main valve16, switches and a drive-in process is triggered.

All the elements ofFIG.1mentioned thus far are only represented schematically. A specific configuration of these elements can, for example, be inferred fromFIGS.1and2of document WO 2019/038124 A1 as well as the corresponding description therein. The design described in the document is suitable for use with the invention.

The elements represented inFIG.1in the cross-section, which are collectively referred to as control valve arrangement, are important for the understanding of the invention. They are responsible for controlling the pressure in the main control line20and thus for triggering drive-in processes. These elements include a first control valve22, a second control valve24, a trigger26and a contact sensor28. In the cross-sectional representation ofFIG.1, only one upper end of the contact sensor28is shown. The contact sensor24also comprises a lower end104, which inFIG.1is represented schematically and protrudes over an opening of an outlet tool not represented. Details on the control valve arrangement will be explained further with reference to the enlarged representation ofFIG.2.

FIG.2shows the control valve arrangement in an initial state of the compressed air nail gun, in which trigger26and contact sensor28are not actuated and the compressed air nail gun is correctly connected to a compressed air source. The housing interior32(which is also only partially represented) arranged inside the housing30, which can only be recognised in sections, is then continuously under operating pressure. The housing30merges, on the right edge ofFIG.2, into a handle section34of the compressed air nail gun.

The trigger26is pivotably mounted on the housing30about an axis36fixed to the housing. At its rear end, it has an actuating surface38by means of which a valve pin40of the first control valve22is movable. The rear end of the contact sensor28interacts with a contact sensor lever42arranged partially inside a recess of the trigger26. At the rear end, the contact sensor lever42is pivotably mounted on the housing30about an axis44fixed to the housing. The front end of the contact sensor lever42is entrained by the rear end of the contact sensor28when the contact sensor28moves upwards relative to the housing30when the compressed air nail gun is placed on a workpiece. As a result, an actuating surface46of the contact sensor lever42moves a valve pin48of the second control valve24upwards.

The first control valve22comprises a lower valve sleeve50and an upper valve sleeve52. A small borehole54is arranged in the transverse direction in the lower valve sleeve50. This borehole54has a diameter of about 70 μm and a length of about 200 μm. Due to these very small dimensions, the borehole54inFIG.2is not to scale, but represented in a slightly enlarged manner. The space56arranged inside the lower valve sleeve50, which adjoins the borehole54, is permanently connected to external air via a transverse borehole106in the upper valve sleeve52and an obliquely arranged borehole108in the housing34. A further, continuous connection between the space56and external air exists via an annular gap58between the valve pin40and the lower valve sleeve50.

In the position of the first control valve22shown, the lower O-ring60is not sealed on the valve pin40, so that the obliquely arranged borehole64and a space66connected to it above a locking sleeve68, which surrounds the second control valve24, are also deaerated via the transverse borehole62in the upper valve sleeve52.

The locking sleeve68is in the indicated initial state in an upper end position in which it is held by the force of a spring70. This upper end position is an open position. A further force on the locking sleeve68is exerted by the pressure in a control volume72, which surrounds the second control valve24in a ring shape. In the indicated initial state, this force is zero because the control volume72has not yet been supplied with compressed air and is connected to external air via the borehole54. In the example represented, the control volume72has a volume in the range between 1 ml and 1.5 ml.

As long as the valve pin48of the second control valve24is in its unactuated position, the lower O-ring74is not sealed on the valve pin48. The upper O-ring76is also not sealed on the valve sleeve78of the second control valve24. Therefore, the main control line20is connected to external air via a transverse borehole80in the locking sleeve68, running past the upper O-ring76, via a transverse borehole82, an annular gap84between valve pin48and valve sleeve78and running past the O-ring74.

If, starting from the state shown inFIG.2, the contact sensor28is actuated, the valve pin48of the second control valve24moves against the force of a spring86into its actuated position shown inFIG.3, in which the O-ring74is sealed. As a result, the main control line20is shut off from external air. In addition, by moving the valve pin48, its upper O-ring88releases the seal, whereby a connection is established between the space66and the main control line20, namely running past the O-ring88, through the transverse borehole82, running past the O-ring76and through the transverse borehole80. As the space66is still depressurised, no drive-in process is triggered yet.

If, in the next step, the trigger26is also actuated, as shown inFIG.4, the valve pin40of the first control valve22is moved into its actuated position and the lower O-ring60creates a seal and an upper O-ring90of the valve pin40releases the seal. As a result, there is a connection between the always aerated housing interior32and the space66via the transverse borehole62in the upper valve sleeve52. This causes immediate aeration of the main control line20via the connection described above, so that a drive-in process is triggered. In addition, the control volume72is aerated via a non-return valve formed by a middle O-ring92on the valve sleeve78. Immediately afterwards, the control volume72is therefore also under operating pressure, just like the space66. The three forces acting on the locking sleeve68continue to act together such that the locking sleeve68remains in its upper end position.

If the compressed air nail gun is then removed from the workpiece, the contact sensor28moves back downwards so that the valve pin48of the second control valve24also returns to its initial position, as shown inFIG.5. As a result, the upper O-ring88of the valve pin48is sealed again so that no further compressed air supply to the main control line20or into the control volume72is possible. The pressure in the control volume72slowly decreases via the borehole54. The main control line20is deaerated with external air via the connection already described inFIG.2.

By re-actuating the contact sensor28, starting from the state ofFIG.5, contact triggering can be carried out at any time because the main control line20can be aerated again by moving the valve pin48upwards. At the same time, the pressure in the control volume72is then refreshed via the non-return valve so that the delay time, within which further contact triggering is possible, starts running again.

However, if the contact sensor28remains unactuated for a certain time when the trigger26is actuated, the pressure in the control volume72falls below a specified pressure threshold. As a result, the balance of the three forces acting on the locking sleeve68changes and the locking sleeve68enters into its lower end position shown inFIG.6. The lower end position is a locked position. In this position of the locking sleeve68, a lower inner circumference of the locking sleeve68seals against the O-ring94so that a compressed air supply to the control volume72via the non-return valve is no longer possible. In addition, the upper O-ring76on the valve sleeve78creates a seal, so that a compressed air supply is also no longer possible via the transverse borehole80to the main control line20.

Furthermore, the space designated by96inFIG.6is connected to external air via a non-visible borehole. Since a middle O-ring98is not sealed on the locking sleeve68, the main control line20is deaerated via the space96. Moving the locking sleeve68into its locked position therefore represents a safety measure which reliably prevents the triggering of a further drive-in process. Further drive-in processes can only be triggered when the trigger26is released and thus the space66is deaerated so that the locking sleeve68moves back into its open position.

A second exemplary embodiment is explained with reference toFIGS.7to10. With regard to the elements schematically represented inFIG.1and with regard to the design of the second control valve24with locking sleeve68, there are no differences in relation to the first exemplary embodiment ofFIGS.1to6. The elements adopted unchanged may be provided with the same reference numerals as in the first exemplary embodiment and will not explained again.

There is a difference with the contact sensor lever42, whose rear end is not fixed to the housing, but is hinged to a rear end of the trigger26. As a result, the valve pin48of the second control valve24is not actuated with each actuation of the contact sensor28, but only when trigger26and contact sensor28are actuated together. In addition, the space66above the locking sleeve68is not aerated via the first control valve22, but is continuously connected to the housing interior32via a borehole100.

The aforementioned changes with respect to the first exemplary embodiment allow a particularly simple configuration of the first control valve22. This control valve comprises a lower valve sleeve50in which the borehole54is arranged, as explained in more detail in the first exemplary embodiment. In contrast to the first exemplary embodiment, the first control valve22exclusively fulfils the object of optionally aerating or deaerating the control volume72via the borehole54. For this purpose, the first control valve22, in its unactuated position indicated inFIG.7running past the upper O-ring102, establishes a connection between the space56of the inside of the lower valve sleeve50and the housing interior32, while the lower O-ring60is sealed. The control volume72is thus slowly aerated through the borehole54. After a certain time has expired, after which the compressed air nail gun has been connected to a compressed air source and during which neither trigger26nor contact sensor28have been actuated, the compressed air nail gun is located in the initial state shown inFIG.7. The control volume72is under operating pressure and the locking sleeve68is in its open position.

FIG.8shows the situation after the trigger26has been actuated. The upper O-ring102of the valve pin40is sealed and the control volume72is slowly deaerated via the borehole54. Thus, the delay time starts to run when the trigger26is actuated.

If the contact sensor28is actuated before expiry of the delay time with the trigger26still actuated, the valve pin48of the second control valve24is moved upwards, as represented inFIG.9. This triggers a drive-in process in the same way as explained in the first exemplary embodiment. As explained in the first exemplary embodiment, the pressure in the control volume72is refreshed via the non-return valve formed by the middle O-ring92.

After lifting the compressed air nail gun from a workpiece, the valve pin48of the second control valve24returns to its unactuated position and the control volume72is slowly deaerated via the borehole54. Provided the pressure threshold in the control volume72is not undercut, the locking sleeve68remains in its open position so that the situation corresponds to that ofFIG.8. Further contact triggering is possible.

However, if the trigger26remains actuated without further triggering occurring within the delay time, the locking sleeve68is moved into its locked position shown inFIG.10, which prevents further triggering in the same way as explained in the first exemplary embodiment. In order to enable further triggering, the trigger26must first be released again and it is necessary to wait until the pressure in the control volume72exceeds the pressure threshold and the locking sleeve68is moved back into its open position. Then, the device is again located in the state where it is ready to be triggered, shown inFIG.8.

In both exemplary embodiments, the housing30has two recesses which receive the first control valve22and the second control valve24. The control volume72is located within the recess, which receives the second control valve24.

LIST OF REFERENCE NUMERALS

10Working piston12Driving ram14Working cylinder16Main valve18Pilot Valve20Main control line22First control valve24Second control valve26Trigger38Contact sensor30Housing32Housing interior34Handle section36Axis38Actuating surface40Valve pin of the first control valve42Trigger lever44Axis46Actuating surface48Valve pin of the second control valve50Lower valve sleeve52Upper valve sleeve54Borehole56Space inside the lower valve sleeve58Annular gap60Lower O-ring62Transverse borehole64Borehole66Space68Locking sleeve70Spring72Control volume74Lower O-ring76Upper O-ring78Valve sleeve80Transverse borehole82Transverse borehole84Annular gap86Spring88Upper O-ring90Upper O-ring92Middle O-ring (non-return valve)94O-ring96Space98Middle O-ring100Borehole102Upper O-ring104Lower end106Transverse borehole108Borehole