Fastening tool comprising a delay unit

Abstract

A fastening tool for driving a fastening element in a driving direction into a workpiece, comprising - a first chamber, wherein the first chamber comprising - a first piston dividing the first chamber into a working volume and a return volume, - a second chamber, wherein the second chamber comprising - a second piston dividing the second chamber into a spring compressing volume and a fastening element feeding volume, - a connecting section located between the first chamber and the second chamber, wherein the connecting section comprising: - a first connecting section connecting the connecting section with the first chamber, - a second connecting section connecting the connecting section with the second chamber, - a delay unit connecting the first connecting section with the second connecting section.

Description

Technical Field

[0001] Described herein is a fastening tool for driving a fastening element in a driving direction into a workpiece, especially a pressure driven fastening tool, comprising a delay unit for preventing a friction between a fastening element and a piston during the return stroke of the first piston and to allowing time for the complete return stroke of the piston. Moreover, a method for delaying a fastening element feeding in a fastening tool is described, too.Background of the Invention

[0002] In many applications, there is the need to join to, or couple with, elements. One such application is joining two elements by driving a fastening element into one or both of the elements, thereby using a fastening tool as mentioned above. The fastening tool is pressed against one of the elements, hereinafter referred to as a workpiece, then a driving mechanism is triggered which may drive a driving element onto the fastening element to drive the fastening element into the workpiece.

[0003] EP2886254 A1 teaches a work tool for driving a securing element into a substructure. The work tool includes a guide channel for the securing element, a piston that is moveable towards the securing element proceeding from a starting position in which the piston is at rest, so as to transmit energy to the securing element arranged in the guide channel, a feed device for conveying the securing element into the guide channel, and a feed-delay device for delaying the securing element being conveyed into the guide channel until the piston has returned into the starting position following a driving process. EP2886254 A1 has the disadvantage that the contact force, that the user must apply to prime the tool by pressing against the material to be fastened into will be higher with the feed-delay device, than without.

[0004] EP1648662 A1 discloses a fastener-driving tool including an integrated function member that performs at least two of the following three functions: a check pawl function, a last fastener-retaining function, and a dry fire lock-out function. In the disclosed embodiment, the integrated function member is provided as a lever-type structure that constitutes part of the access door assembly by means of which access is gained to the fastener drive track along which fasteners (e.g., roofing nails) are fed to the driving portion of the tool. Also disclosed is an improved method of retaining the last nail in the drive track by a lateral head gripping action and a tool for performing the method. EP1648662 A1 has the disadvantage that the force required to transport the fasteners is applied already during the phase when the piston is returning to the back of the tool. The moving piston es subjected to friction by the fastener pressed against it, while it is moving.

[0005] EP2162264 A1 discloses a fastener driving tool including a power source including a reciprocating driver blade, a tool nose associated with the power source for receiving the driver blade for driving fasteners fed into the nose, a magazine constructed and arranged to house a supply of the fasteners, a magazine feeder mechanism associated with the magazine for sequentially feeding fasteners into the nose, the feeder mechanism including a reciprocating feed piston, and an electromechanical retention device that is operationally associated with the feeder mechanism and configured for retaining the feed piston in a retracted position until the driver blade is positioned to allow fastener advancement into the nose. EP2162264 A1 describes a setup, where an electromagnet holds a fastener transport mechanism, while this is being biased by loaded spring. This is an additional electric consumer, that draws energy from the battery. It reduces the run time of the tool battery, causing the user to more often need to recharge.Summary of the Invention

[0006] An object of the present invention is to overcome at least one of the disadvantages of the prior art. It is further an object of the present invention to provide a fastening tool for driving a fastening element in a driving direction into a workpiece, especially a pressure driven fastening tool, comprising a delay unit for preventing a friction between a fastening element and a piston during the return stroke of the piston and to allowing time for the complete return stroke of the piston.

[0007] At least one of these objects has been solved by the features of the independent patent claims. Other preferred embodiments are indicated in the dependent claims and in this summary of the invention.

[0008] In a first aspect of the present invention, the object is achieved by a fastening tool for driving a fastening element in a driving direction into a workpiece, comprising a first chamber, wherein the first chamber comprising a first piston dividing the first chamber into a working volume and a return volume, a second chamber, wherein the second chamber comprising a second piston dividing the second chamber into a spring compressing volume and a fastening element feeding volume, a connecting section located between the first chamber and the second chamber, wherein the connecting section comprising: a first connecting section connecting the connecting section with the first chamber, a second connecting section connecting the connecting section with the second chamber, a delay unit connecting the first connecting section with the second connecting section.

[0009] The term "first chamber" comprises a part or a section of the fastening tool in which a first piston - also known as a working piston - is located.

[0010] The term "first piston" refers to a part of the fastening tool that transfers energy from an energy storage to the fastening element. The first piston is configured to move within the first chamber along the driving direction between an initial position and a driving position. The working piston also has a rear end in the driving direction. At the rear end the first piston divides the first chamber into a working volume (behind the rear end) and a return volume (before the rear end), wherein the first piston is configured to move within the first chamber along the driving direction.

[0011] The term "working volume" comprises a volume within the first chamber wherein energy for driving a fastening element in a driving direction is released. The working volume is connected, with a dose chamber, which is located adjacent to the working volume and comprises high-pressure air. To drive the fastening element in the driving direction into the workpiece a user of the fastening tool must compress a nose of the tool on the workpiece and must pull a trigger. If the user pulls the trigger, the dose chamber is closed, and a hammer is activated. The term "hammer" comprises a part of the fastening tool, which can move along or parallel the driving direction and is in physical contact with a valve of the dose chamber. If the hammer gets activated, the hammer hits the valve of the dose chamber and a defined amount of the high-pressure air within the dose chamber flows into the working volume and a working pressure - for driving the first piston - is generated within the working volume.

[0012] The term "return volume" comprises a volume within the first chamber which is configured for returning the first piston from the driving position to the initial position. The return volume is the volume before the rear end of the first piston along the driving direction. The first chamber further comprises a return chamber adjacent to the return volume. The return volume is connected to the return chamber by means of at least one orifice at an end of the return volume. The main difference between the return volume and the return chamber is that the first piston moves only within the return volume but not within the return chamber. Nevertheless, the return volume and the return chamber both configured for returning the first piston from the driving position to the initial position.

[0013] The term "second chamber" comprises a part or a section of the fastening tool in which a second piston - also known as a fastening element feeding piston - is located.

[0014] The term "second piston" refers to a part of the fastening tool that provides the first piston with the fastening element in front of the first piston when the first piston is in the initial position and ready for driving a fastening element into a workpiece. If the second piston provides the fastening element too early to the first piston, for example if the first piston is not returned to the initial position, yet, the fastening element will create a friction on the first piston. The second piston is configured to move within the second chamber along a fastening element feeding direction between a compressed position and an extended position. The second piston also has a rear end in the fastening element feeding direction. At the rear end the second piston divides the second chamber into a fastening element feeding volume (behind the rear end) and a spring compressing volume (before the rear end), wherein the second piston is configured to move within the second chamber along the fastening element feeding direction.

[0015] The term "fastening element feeding volume" comprises a volume within the second chamber which is located behind the rear of the second piston, wherein energy for driving a fastening element in a fastening element feeding direction is stored and released within the fastening element feeding volume. The fastening element feeding volume comprises a spring which stores energy if the second piston is moved against the fastening element feeding direction and releases said energy if the second piston is moved along the fastening element feeding direction.

[0016] The term "spring compressing volume" comprises a volume which is in front of the rear of the second piston within the second chamber which is configured for returning the second piston from the extended position to the compressed position. The spring compressing volume is the volume before the rear end of the second piston along the fastening element feeding direction.

[0017] The term "connecting section" describes a section between the first chamber and the second chamber, wherein the connecting section comprises a fluid communication between the first chamber and the second chamber.

[0018] The term "first connecting section" describes a sub-section of the connecting section which is directly connected with the first chamber and comprises a fluid communication with the first chamber.

[0019] The term "second connecting section" describes a further sub-section of the connecting section which is directly connected with the second chamber and comprises a fluid communication with the second chamber.

[0020] The term "delay unit" refers to a unit which is located between the first connecting section and the second connecting section and comprises a fluid communication between the first connecting section and the second connecting section.

[0021] The technical effect of said first aspect of the present invention is, that due to the fastening element delay unit between the first chamber and the second chamber the time in which the fastening element feeding volume is compressed is shorter than the time in which the same volume is expanded. In other words, the second piston moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a fastening element and the first piston during the return stroke of the first piston is prevented.

[0022] A further technical effect of said first aspect of the present invention is, that due to the fluid communication between the first chamber and the second chamber the return of the first piston not only provided by the return volume and the return chamber but is also assisted by the second chamber. Hence, the first piston is fully returned to the initial position when the fastening element is provided by the second piston in front of the first piston.

[0023] Optionally the delay unit can be placed in the first connecting section or the second connecting section or the first chamber or the second chamber.

[0024] In an advantageous embodiment said delay unit is configured to allow a first gas flow from the first chamber to the second chamber and a second gas flow from the second chamber to the first chamber.

[0025] The term "gas flow" refers generally to a movement of gas molecules through a system, primarily driven by differences in pressure. This movement occurs as gas molecules travel from regions of higher pressure to regions of lower pressure. The characteristics of said gas flow, such as flow rate, velocity, and direction, are significantly influenced by these pressure differentials. The gas flow from the first chamber to the second chamber and the gas flow from the second chamber to the first chamber is part of the fluid communication with in the fastening tool.

[0026] The term "first gas flow" refers to a movement from the first chamber to the second chamber. In context of this invention a first gas flow occurs if the pressure in the first chamber is greater than the pressure in the second chamber and the first chamber and the second chamber comprising a fluid communication to each other.

[0027] The term "second gas flow" refers to a movement from the second chamber to the first chamber. In context of this invention a second gas flow occurs if the pressure in the second chamber is greater than the pressure in the first chamber and the first chamber and the second chamber comprising a fluid communication to each other.

[0028] The technical effect of said advantageous embodiment is, the time in which the fastening element feeding volume is compressed is shorter than the time in which the same volume is expanded. In other words, the second piston moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a fastening element and the first piston during the return stroke of the first piston is prevented.

[0029] A further technical effect of said advantageous embodiment is, that due to the fluid communication between the first chamber and the second chamber the return of the first piston not only provided by the return volume and the return chamber but is also assisted by the second chamber. Hence, the first piston is fully returned to the initial position when the fastening element is provided by the second piston in front of the first piston.

[0030] In an advantageous embodiment the delay unit is configured to allow the first gas flow from the first chamber to the second chamber if a working pressure in the working volume is greater than a return pressure in the return volume and the second gas flow from the second chamber to the first chamber if a working pressure in the working volume is less than a return pressure in the return volume.

[0031] The term "working pressure" refers to the pressure within the working volume. The term "return pressure" refers to the pressure within the return volume and the return chamber. The generation of the first gas flow and the second gas flow can be described in four stages each from the perspective of the first piston.Stage 1 - First piston in initial position and start of moving in the driving direction

[0032] If the first piston reaches the initial position and the user pulls the trigger of the fastening tool, the working pressure can reach values between 20 bar and 40 bar and the return pressure is at atmospheric pressure. In this case the working pressure is greater than the return pressure and the first piston is forced to move in the driving direction within the first chamber (stage 1). Simultaneously the pressure in the return volume and the return chamber is increased due to the movement of the first piston in the driving direction. The second piston stays at the extended position.

[0033] The first chamber comprises a first interface which connects the first chamber to the connecting section. The term "first interface" refers to an interface that comprises the shortest distance to the initial position of the first piston within the first chamber. Said first interface allows a gas flow to exit the first chamber and enter the first connecting section or allows the gas flow to exit the first connecting section and enter the first chamber.Stage 2- First piston exceeds first interface in the driving direction

[0034] If the first piston is forced to move in the driving direction within the first chamber the first piston will pass the first interface, and the working volume will be directly connected with the first connecting section (stage 2). In other words: If the first piston passes the first interface in the driving direction, the first connecting pressure within the first connecting section rises immediately to a value between 2 bar and 8 bar, preferable 6 bar. This generates a first gas flow from the working volume of the first chamber to the spring compressing volume of the second chamber.

[0035] In the next step the first gas flow enters the delay unit and the second chamber. The delay unit comprises in this stage a first gas flow resistance which is relatively low due to the high pressure in the delay unit.

[0036] If the first gas flow enters the second chamber, the first gas flow forces the second piston to move against the fastening element feeding direction. Hence, the spring compressing volume is expanded and the fastening element feeding volume is compressed. In other words: the spring within the fastening element feeding volume gets compressed and stores energy which is released at a later stage.Stage 3- First piston reaches the driving position

[0037] In the meantime, the first piston reaches the driving position and between the working volume of the first chamber and the spring compressing volume of the second chamber a pressure equilibrium is generated (stage 3). In other words: the first gas flow is interrupted by the pressure equilibrium and at this stage no gas flow between the first chamber and the second chamber exists. In this stage the second piston reaches the compressed position and the spring within the fastening element feeding volume is now fully compressed.Stage 4 - First piston returns from the driving position to the initial position

[0038] To return the first piston from the driving position back to the initial position the working pressure in the working volume is released through an opening to the atmosphere when the tool is no longer compressed. This results in a working pressure which is less than the return pressure in the return volume and the return chamber. In other words: The first piston is forced to move from the driving position to the initial position.

[0039] At the beginning of this stage the working volume of the first chamber is still connected through the first interface with the spring compressing volume of the second chamber. In the moment, when the working pressure in the working volume is released through an opening to the atmosphere the pressure equilibrium is interrupted, and a second gas flow from the second chamber to the first chamber is generated due to energy which is released from the spring to the second piston. This results in a higher spring compressing pressure in the spring compressing volume in the second chamber compared to the working pressure of the in the working volume in the first chamber.

[0040] In the next step the second gas flow enters the delay unit and the first chamber. The delay unit comprises in this stage a second gas flow resistance which is higher as the first gas flow resistance in stage 2.

[0041] The technical effect of said advantageous embodiment is, that the time in which the fastening element feeding volume is compressed is shorter than the time in which the same volume is expanded. In other words, the second piston moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a fastening element and the first piston during the return stroke of the first piston is prevented.

[0042] A further technical effect of said advantageous embodiment is, that due to the fluid communication between the first chamber and the second chamber the return of the first piston not only provided by the return volume and the return chamber but is also assisted by the second chamber. Hence, the first piston is fully returned to the initial position when the fastening element is provided by the second piston in front of the first piston.

[0043] In an advantageous embodiment said the delay unit is configured to allow the first gas flow from the first chamber to the second chamber if a fastening element feeding pressure in the fastening element feeding volume is less than a spring compressing pressure in the spring compressing volume and the second gas flow from the second chamber to the first chamber if a fastening element feeding pressure in the fastening element feeding volume is higher than a spring compressing pressure in the spring compressing volume.

[0044] The technical effect of said advantageous embodiment is, that the time in which the fastening element feeding volume is compressed is shorter than the time in which the same volume is expanded. In other words, the second piston moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a fastening element and the first piston during the return stroke of the first piston is prevented.

[0045] A further technical effect of said advantageous embodiment is, that due to the fluid communication between the first chamber and the second chamber the return of the first piston not only provided by the return volume and the return chamber but is also assisted by the second chamber. Hence, the first piston is fully returned to the initial position when the fastening element is provided by the second piston in front of the first piston.

[0046] In an advantageous embodiment said wherein the delay unit comprising a hollow space, a throttle element placed in the hollow space.

[0047] The term "hollow space" refers to spatial arrangement within the delay unit where elements - in this case the throttle element - can be placed independently of the shape or state of said element.

[0048] The term the "throttle element" refers to an element comprising at least one gas flow resistance and said throttle element can change said gas flow resistance based on flow conditions, especially flow pressure.

[0049] The technical effect of said advantageous embodiment is, that if a first gas flow is generated, the throttle element adjusts the gas flow resistance to the first gas flow resistance. This leads to a strong first gas flow from the first chamber to the second chamber. If the first gas flow stops or if the second gas flow is generated, the throttle element adjusts the gas flow resistance to the second gas flow resistance. This leads to a weaker second gas flow from the second chamber to the first chamber.

[0050] Optionally the second gas flow resistance - the gas flow resistance which occurs for the second gas flow - is the default gas flow resistance. Hence, when the user starts working with the fastening tool, the throttle element comprises the second gas flow resistance.

[0051] In an advantageous embodiment said throttle element comprising a first state and a second state.

[0052] The term "first state" refers to the shape of the throttle element if the first gas flow occurs. The term "second state" refers to the shape of the throttle element if the second gas flow or no gas flow occurs. The second state is the default state of the throttle element.

[0053] The technical effect of said advantageous embodiment is, that if a first gas flow is generated, the throttle element adjusts the gas flow resistance to the first gas flow resistance and also changes the state to the first state. This leads to a strong first gas flow from the first chamber to the second chamber. If the first gas flow stops or if the second gas flow is generated, the throttle element adjusts the gas flow resistance to the second gas flow resistance and also changes the state to the second state. This leads to a weaker second gas flow from the second chamber to the first chamber.

[0054] In an advantageous embodiment said throttle element further comprising an intersection opening, wherein said intersection opening of the first state of the throttle element is greater than the intersection opening of the second state of the throttle element.

[0055] The term "intersection opening" refers to a transition volume of the throttle element which comprises at least the transition of the first gas flow from the first connecting section to the delay unit and the transition of the second gas flow from the delay unit to the first connecting section.

[0056] The technical effect of said advantageous embodiment is, that if a first gas flow is generated, the size of the intersection area is increased and therefore the first gas flow resistance is decreased. This leads to a strong first gas flow from the first chamber to the second chamber. If a second gas flow is generated, the size of the intersection area is smaller and therefore the second gas flow resistance is higher than the first gas flow resistance. This leads to a weaker second gas flow from the second chamber to the first chamber.

[0057] In an advantageous embodiment said throttle element further comprising a trimmed section allowing the intersection opening to change from the first state to the second state or to change from the second state to the first state.

[0058] The term "trimmed section" refers to a part of the throttle element which is trimmed, cut or perforated. Due the trimmed section the throttle element can partly change its shape which leads to different states of the intersection opening.

[0059] The technical effect of said advantageous embodiment is, that due to a high pressure of the first gas flow the trimmed section changes the shape of the throttle element if the first gas flow passes said throttle element. The shape of the throttle element changes such, that the first gas flow resistance is less than the second gas flow resistance. In other words, if the second gas flow passes the trimmed section the second gas flow resistance is increased.

[0060] In an advantageous embodiment said intersection opening is surrounded by the trimmed section and the trimmed section is a circle cutout.

[0061] The term "circle cutout" refers to the shape of the trimmed section. In this case the trimmed section is a circular section but not completely close. Hence, the shape of the trimmed section follows partly the shape of a circle.

[0062] The technical effect of said advantageous embodiment is, that due to a high pressure of the first gas flow the trimmed section changes the shape of the throttle element if the first gas flow passes said throttle element. The shape of the throttle element changes such, that the first gas flow resistance is less than the second gas flow resistance. A further technical effect of said advantageous embodiment is, that due to the circle cut out the throttle element can restore its initial shape if the first gas flow does not occur, or the second gas flow occurs. This leads to different gas flow resistances of the throttle element.

[0063] In an advantageous embodiment said circle cutout comprising a circle cutout center and the intersection opening is placed in the circle cutout center. The term "circle cutout center" refers to the middle point of a circle which the circle cutout covers partly.

[0064] The technical effect of said advantageous embodiment is, that if the circle cutout center is congruent with the intersection opening a more uniform change from the second state of the throttle element to the first state of throttle element is generated. A further technical effect of said advantageous embodiment is that the throttle element can achieve a smaller size and therefore is easier to integrate within the fastening tool.

[0065] In an advantageous embodiment said throttle element comprising a foldable section. The term "foldable section" refers to a part of the throttle element which is - based on the flow conditions and / or state of the throttle element - foldable. The foldable section is generated by the trimmed section.

[0066] The technical effect of said advantageous embodiment is, that a difference in the first gas flow resistance and the second gas flow resistance can be easily realized by a foldable section. A further technical effect of said advantageous embodiment is that the first gas flow and the second gas flow, can at least partly pass the delay unit through the same gas flow path. In other words: The path for the first gas flow and the second gas flow do not need to be separated.

[0067] In an advantageous embodiment said throttle element comprising a throttle element center and the circle cutout center is placed in the throttle element center.

[0068] The technical effect of said advantageous embodiment is, that if the circle cutout center is congruent with the throttle element center a more uniform change from the second state of the throttle element to the first state of throttle element is generated. A further technical effect of said advantageous embodiment is that the throttle element can achieve a smaller size and therefore is easier to integrate within the fastening tool.

[0069] In a second aspect of the present invention, the object is achieved by a method for delaying a fastening element feeding in a fastening tool comprising the steps of: providing a fastening tool for driving a fastening element in a driving direction into a workpiece, wherein the fastening tool comprising a first chamber, wherein the first chamber comprising a first piston dividing the first chamber into a working volume and a return volume, a second chamber, wherein the second chamber comprising a second piston dividing the second chamber into a spring compressing volume and a fastening element feeding volume, a connecting section located between the first chamber and the second chamber, wherein the connecting section comprising: a first connecting section connecting the connecting section with the first chamber, a second connecting section connecting the connecting section with the second chamber, a delay unit connecting the first connecting section with the second connecting section and comprising a hollow space and a throttle element placed in the hollow space, wherein said throttle element comprising a first state and a second state, generating a first gas flow from the first chamber to the second chamber, changing the throttle element from the second state to the first state.

[0070] The technical effect of said advantageous second aspect of the present invention is that if a first gas flow is generated, the throttle element adjusts the gas flow resistance to the first gas flow resistance. This leads to a change from the second state to the first state of the throttle element and leads to a strong first gas flow from the first chamber to the second chamber.

[0071] In an advantageous embodiment said method further comprising the steps of reaching a pressure balance between the first chamber and the second chamber, changing the throttle element from the first state to the second state.

[0072] The technical effect of said advantageous embodiment is, that by reaching the pressure balance between the first chamber and the second chamber, the first gas flow stops and the throttle element changing from the first state to the second state. This leads a change in gas flow resistance from the first gas flow resistance to the second gas flow resistance.

[0073] In an advantageous embodiment said method further comprising the steps of generating a second gas flow from the second chamber to the first chamber.

[0074] The technical effect of said advantageous embodiment is, that by generating the second gas flow the time in which the fastening element feeding volume is compressed is shorter than the time in which the same volume is expanded. In other words, the second piston moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a fastening element and the first piston during the return stroke of the first piston is prevented.

[0075] Further optional embodiments follow which can be combined or specified as desired with all previous embodiments of the first and second aspect and also with all further optional embodiments of the first and second aspect.

[0076] In further optional advantageous embodiment said circle cutout comprising at least one of the following values: i. 270°, ii. 275°, iii. 280°, iv. 285°, v. 290°, vi. 295°, vii. 300°, viii. 305°, ix. 310°, x. 315°, xi. 320°.

[0077] The circle cutout does not exceed the value of 320° because a minimum amount of a not cut section is needed that the throttle element is enabled to change into the first state. The circle cutout needs to exceed at least 180°, otherwise the first state of the throttle element cannot be reached.

[0078] The technical effect of said further optional advantageous embodiment is, that comprising at least one of the values above the circle cutout enables the throttle element to change from the second state to the first state.

[0079] In further optional advantageous embodiment said trimmed section overlaps said intersection opening.

[0080] The term " said trimmed section overlaps said intersection opening " refers to the fact that an adjacent part of the intersection opening is trimmed.

[0081] The technical effect of said further optional advantageous embodiment is, that the intersection opening changes the size and the shape in the first state of the throttle element. This leads to an enhanced size of the intersection opening due to the adjacent trimmed part which is widen during the first state of the throttle element.

[0082] In further optional advantageous embodiment said connecting section further comprising a check valve allowing the first gas flow additional to the delay unit through said check valve and allowing the second gas flow only through the delay unit.

[0083] The technical effect of said further optional advantageous embodiment is, that the first gas flow receives a further path to reach the second chamber which decreases the first gas flow resistance. The second gas flow resistance is enhanced by the restriction of the second gas flow only be allowed to flow through the delay unit.Brief Description of the Drawings

[0084] Further aspects and advantages of the fastening tool, associated parts and a method of use thereof will become apparent from the ensuing description that is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a state-of-the-art fastening tool. Figure 2 shows an improvement of the state-of-the-art fastening tool according to the invention using a delay unit. Figure 3 shows a pressure curve in front of the delay unit. Figure 4 shows a first embodiment of a throttle element according to the invention. Figure 5 shows a first embodiment of a delay unit according to the invention. Figure 6 shows a second embodiment of a throttle element according to the invention. Figure 7 shows a second embodiment of a delay unit according to the invention. Figure 8 shows a further improvement of the state-of-the-art fastening tool according to the invention using a delay unit and a check valve. Detailed Description

[0085] Figure 1 shows a state-of-the-art fastening tool 100. The fastening tool 100 comprising a first section chamber 101 and a second chamber 102. The first chamber 101 is connected to the second chamber 102 by the connecting section 103.

[0086] The first chamber 101 is divided by the first piston 109 into a working volume 105 and a return volume 107. The return volume 107 is connected to the return chamber 111 by an orifice 131. The first piston 109 is configured to drive a fastening element 121 along a fastening direction 190 into a workpiece (not shown).

[0087] The second chamber 102 is divided by the second piston 113 into a fastening element feeding volume 117 and a spring compressing volume 115. The fastening element feeding volume 117 comprises a spring 133. The second piston 113 is configured to feed the first piston 109 with a next fastening element 123 along a fastening element feeding direction 191.

[0088] The connecting section 103 is directly connected to the return chamber 111 of the first chamber 101 and to the spring compressing volume 115 of the second chamber 102.

[0089] Figure 1a shows how the first piston 101 moves in the driving direction 190. The pressure in the return volume 107 and the return chamber 109 are increasing due to the movement of the first piston 101. Since, the connecting section 103 is directly connected to the return chamber 111 and to the spring compressing volume 115, the pressure in the spring compressing volume 115 rises and forces the second piston 113 to move against the fastening element feeding direction 191. As a result, the spring 133 and the fastening element volume 117 are getting compressed.

[0090] Figure 1b shows the first piston 101 in the driving position when a fastening element 121 is fixed to a workpiece (not shown). During movement along the driving direction 190 the first piston 109 passes a check valve 167 which opens when the working pressure in the working volume 105 gets in contact with the check valve 167. This results in an even further increase of pressure in the return volume 107 and the return chamber 111 when the first piston 109 is in the driving position. Since, the connecting section 103 is directly connected to the return chamber 111 and to the spring compressing volume 115, the pressure in the spring compressing volume 115 rises and forces the second piston 113 to move further against the fastening element feeding direction 191. As a result, the spring 133 and the fastening element volume 117 are getting compressed and the second piston 113 reaches a compressed position.

[0091] Figure 1c shows how the working pressure in the working volume 105 is released to the atmosphere and decreases the working pressure in the working volume 105. The pressure in the return volume 107 and in the return chamber 111 are now exceeding the working pressure in the working volume 105 and the first piston 109 is moved back form the driving position to the initial position. The check valve 167 closes again due to the higher pressure in the return chamber 111 compared to the pressure in the working volume 105. Since, the connecting section 103 is directly connected to the return chamber 111 and to the spring compressing volume 115, the pressure in the fastening element feeding volume 117 forces the second piston 113 to move in the fastening element feeding direction 191. As a result, the spring 133 and the fastening element volume 117 are expanding and the second piston 113 is starting to direct the next fastening element 123 towards the first piston 109.

[0092] Figure 1d shows how the first piston 109 moves against the driving direction 190. The first piston 109 did not reach the initial position yet. The next fastening element 123 has been already pushed from the second piston 113 against the first piston 109 which results in high friction and also less reliability of a state-of-the-art fastening tool. How to avoid said friction between the first piston 109 and the next fastening element 123 is shown in Figure 2.

[0093] Figure 2 shows an improvement of the state-of-the-art fastening tool 591 according to the invention using a delay unit 219.

[0094] The driving tool 591 comprising a first section chamber 201 and a second chamber 202. The first chamber 201 is connected to the second chamber 202 by the connecting section 203.

[0095] The first chamber 201 is divided by the first piston 209 into a working volume 205 and a return volume 207. The return volume 207 is connected to the return chamber 211 by an orifice 231. The first piston 209 is configured to drive a fastening element 221 along a fastening direction 290 into a workpiece (not shown).

[0096] The second chamber 202 is divided by the second piston 213 into a fastening element feeding volume 217 and a spring compressing volume 215. The fastening element feeding volume 217 comprises a spring 233. The second piston 213 is configured to feed the first piston 209 with a next fastening element 223 along a fastening element feeding direction 291.

[0097] The connecting section 203 is directly connected to the first chamber 201 with a first interface 235. Further, the connecting section 203 is directly connected to the spring compressing volume 215 of the second chamber 202. The connecting section 203 comprises a first connecting section 237 which is directly connected with the first chamber 201 and comprises a fluid communication with the first chamber 201. The connecting section 203 comprises further a second connecting section 239 which is directly connected with the second chamber 202 and comprises a fluid communication with the second chamber 202. A delay unit 219 is placed between the first connecting section 237 and the second connecting section 239 and comprises a fluid communication between the first connecting section 237 and the second connecting section 239.

[0098] The working principle of the improvement state-of-the-art fastening tool 591 according to the invention can be described in four stages:

[0099] Figure 2a shows how the first piston 209 moves in the driving direction 290. The pressure in the return volume 207 and the return chamber 211 are increasing due to the movement of the first piston 201. In Figure 2a the connecting section 203 is not directly connected with the return chamber 211. The connecting section 203 has a direct fluid communication either with the working volume 205 or with the return volume 207 (stage 1). In the case of Figure 2a the connecting section is neither connected with the working volume 205 nor with the return volume 207 (stage 1).

[0100] Figure 2b shows that the first piston 209 is forced to move in the driving direction 290 within the first chamber 201. The first piston 209 passed the first interface 235, and the working volume 205 is directly connected with the first connecting section 237 (stage 2). This results in the same pressure within the working volume 205 and the first connecting section 237. This generates a first gas flow 241 from the working volume 205 of the first chamber 201 to the spring compressing volume 215 of the second chamber 202.

[0101] The first gas flow 241 enters the delay unit 219 and the second chamber 202. The delay unit 219 comprises in this stage a first gas flow resistance which is relatively low due to the high pressure in the delay unit 219.

[0102] In the meantime, the first piston 209 reaches the driving position and between the working volume 205 of the first chamber 201 and the spring compressing volume 215 of the second chamber 202 a pressure equilibrium is generated (stage 3, not shown). In other words: the first gas flow 241 is interrupted by the pressure equilibrium and at this stage no gas flow between the first chamber 201 and the second chamber 202 exists. In this stage the second piston 213 reaches the fully compressed position and the spring 233 within the fastening element feeding volume 217 is now fully compressed.

[0103] Figure 2c shows how the working pressure in the working volume 205 is released to the atmosphere and decreases the working pressure in the working volume 205. The pressure in the return volume 207 and in the return chamber 211 are now exceeding the working pressure in the working volume 205 and the first piston 209 is moved back form the driving position to the initial position. The check valve 267 closes again due to the higher pressure in the return chamber 211 compared to the pressure in the working volume 205. Since, the connecting section 203 is directly connected to the working volume 205 of the first chamber 201 a second gas flow 242 is generated from the spring compressing volume 215 of the second chamber 202 to the working volume 205 of the first chamber 201. (stage 4). As a result, the pressure in the fastening element feeding volume 217 forces the second piston 213 to move in the fastening element feeding direction 291. As a result, the spring 233 and the fastening element volume 217 are expanding and the second piston 213 is starting to direct the next fastening element 223 towards the first piston 209

[0104] Figure 2d shows how the first piston 209 passes the first interface 235. The first connecting section 237 is now in fluid communication with the return volume 207 of the first chamber 201. Hence, the second chamber 202 now directly supports the return volume 207 and the return chamber 211 in returning the first piston 209 to the initial position. Since the second gas flow 242 is much weaker than the first gas flow 241, the feeding of the next fastening element 223 to the first piston 209 is significantly delayed. Hence a friction between the first piston 209 and the next fastening element 223 is avoided.

[0105] Figure 3 shows a pressure curve in front of the delay unit 219. The pressure curve 31 shows the pressure over time measured in front of the delay unit 219.

[0106] The pressure curve 31 comprises four stages. In stage 1 the first piston 209 did not pass the first interface 235, yet. Hence, the first connecting section 237 does not comprise a fluid connection to the working volume 205, yet. This results in a constant pressure in the first connecting section 237 during stage 1.

[0107] Once the first piston 209 passes the first interface 235 in the driving direction 290, the pressure in the first connecting section 237 rises rapidly. This position of the first piston 209 defines the transition from stage 1 to stage 2.

[0108] In stage 2 the pressure curve 31 shows a rapid increase of the pressure in the first connecting section 237 followed by a less rapid decrease of the pressure in the first connecting section 237. Due to the pressure rise in the first connecting section 237 the pressure in the delay unit 219 rises accordingly.

[0109] In the next step, the generated first gas flow 241 enters the delay unit 219 and the second chamber 202. The delay unit 219 comprises in this stage a first gas flow resistance which is relatively low due to the high pressure in the delay unit 219.

[0110] If the first gas flow 241 enters the second chamber 202, the first gas flow 241 forces the second piston 213 to move against the fastening element feeding direction 291. Hence, the spring compressing volume 215 is expanded and the fastening element feeding volume 217 is compressed. In other words: the spring 233 within the fastening element feeding volume 217 gets compressed and stores energy which is released at a later stage.

[0111] In stage 3 the pressure curve 31 shows a constant value which corresponds to a pressure equilibrium between the working volume 205 of the first chamber and the spring compressing volume of the second chamber 215. In other words: the first gas flow 241 is interrupted by the pressure equilibrium (stage 3) and at this stage no gas flow between the first chamber 201 and the second chamber 202 exists. In this stage the second piston 213 reaches the compressed position and the spring 233 within the fastening element feeding volume 217 is now fully compressed. At the same time, the first piston 209 reaches the driving position.

[0112] Stage 4 of the pressure curve 31 can be subdivided in several sub-parts. First, the pressure curve 31 drops from the pressure equilibrium due to the fact, that the first piston 209 is forced back from the driving position to the initial position. The working volume 205 comprises a working pressure equal to the atmosphere pressure. Since the pressure in the second chamber 202 and in the first connecting section 203 is higher than the working pressure in the working volume 205, a second gas flow 242 from the second chamber 202 to the first chamber 201 is generated. Due to the second gas flow 242 the pressure drops in the pressure curve 31 after the pressure equilibrium and the second flow 242 directly enters the working volume 205 of the first chamber 201.

[0113] When the first piston 209 is moving against the driving direction 290, the first piston 209 covers the first interface 235 at a certain point. At this point the pressure curve 31 shows a short pressure equilibrium again.

[0114] When the first piston 209 moves further against the driving direction 290 and passes the first interface 235 at a certain point, another pressure drop can be seen at the pressure curve 31. Due to this pressure drop in the pressure curve 31 the second gas flow 242 directly enters the return volume 207 of the first chamber 201.

[0115] In conclusion Figure 3 shows that the time t 2 in stage 2 is significantly shorter than the time t 4 in stage 4. This results in the fact that the time t 2 in which the fastening element feeding volume 217 is compressed is shorter than the time t 4 in which the same volume is expanded. In other words, the second piston 213 moves faster from the extended position to the compressed position as from the compressed position to the extended position. Hence, friction between a next fastening element 223 and the first piston 209 during the return stroke of the first piston 209 is prevented.

[0116] Figure 4 shows a first embodiment of a throttle element 40 according to the invention. Fig.4 shows the front view, and a side cut view A-A through the throttle element 40. The throttle element 40 comprises a disc shape. The throttle element 40 comprises an intersection opening 41 placed in the middle 45 of the throttle element 40. In this embodiment the intersection opening is circular and comprises a diameter of 0.7 mm. The throttle element further comprises a circle cutout 43 which surrounds the intersection opening 41. The part of the circle which is not covered by the circle cutout is shown by the non-trimmed section 47.

[0117] The side cut view A-A through the throttle element 40 displays the thickness T of the throttle element and a radius R of the circle cutout. In this embodiment the thickness T of the throttle element comprises a value of 0.8 mm and the radius R of the circle cutout has a value of 2.5mm.

[0118] Figure 5 shows a first embodiment of a delay unit 50 according to the invention. The delay unit 50 comprises the throttle element 40 according to Figure 4.

[0119] Figure 5a shows a first gas flow 241 from the first connecting section 237 to the second connecting section 239, wherein the first connecting section 237 comprises a diameter 53 and the second connecting section comprises a diameter 57.

[0120] Due to the high pressure in the first connecting section 237 the throttle element 40 changes from the second state to the first state. In the first state the first gas flow 241 does not pass through the intersection opening 41 but through the folded section 244. This leads to a reduced first gas flow resistance.

[0121] Figure 5b shows a second gas flow 242 from the second connecting section 239 to the first connecting section 237. Due to the flow direction the throttle element 40 is connected against the wall 246 and cannot be folded in the direction of the second gas flow 242. Moreover, the throttle element 40 comprises in this second state a higher gas flow resistance compared to the first state of Figure 5a.

[0122] In the second state the second gas flow 242 does pass through the intersection opening 41. This leads to a higher second gas flow resistance .

[0123] Figure 6 shows a second embodiment of a throttle element 60 according to the invention. Figure 6 shows the front view, and a side cut view A-A through the throttle element 60. The throttle element 60 comprises an intersection opening 61 placed in the middle 65 of the throttle element 60. In this embodiment the intersection opening is circular and comprises a diameter of 1.0 mm. The throttle element further comprises a trimmed section 63 which overlaps the intersection opening 61.

[0124] The side cut view A-A through the throttle element 60 displays the thickness T of the throttle element. In this embodiment die thickness T of the throttle element comprises a value of 0.6 mm.

[0125] Figure 7 shows a second embodiment of a delay unit 70 according to the invention. The delay unit 70 comprises the throttle element 60 according to Figure 6.

[0126] Figure 7a shows a first gas flow 241 from the first connecting section 237 to the second connecting section 239, wherein the first connecting section 237 comprises a diameter 73 and the second connecting section comprises a diameter 77.

[0127] Figure 7b shows the delay unit 70 in a front view and in the second state of the throttle element 60. The throttle element 60 comprises an intersection opening 61 placed in the middle 65 of the throttle element 60. In this embodiment the intersection opening is circular and comprises a diameter of 1.0 mm. The throttle element further comprises a trimmed section 63 which overlaps the intersection opening 61.

[0128] Figure 7c shows the delay unit 70 in a front view and in the first state of the throttle element 60. The throttle element 60 comprises an enhanced intersection opening 61 due to the high pressure in the first connecting section 237.

[0129] Figure 8 shows a further improvement of the state-of-the-art fastening tool 800 according to the invention using a delay unit 819 and a delay unit check valve 899.

[0130] The driving tool 800 comprising a first section chamber 801 and a second chamber 802. The first chamber 801 is connected to the second chamber 802 by the connecting section 803.

[0131] The first chamber 801 is divided by the first piston 809 into a working volume 805 and a return volume 807. The return volume 807 is connected to the return chamber 811 by an orifice 831. The first piston 809 is configured to drive a fastening element 821 along a fastening direction 890 into a workpiece (not shown).

[0132] The second chamber 802 is divided by the second piston 813 into a fastening element feeding volume 817 and a spring compressing volume 815. The fastening element feeding volume 817 comprises a spring 833. The second piston 813 is configured to feed the first piston 809 with a next fastening element 823 along a fastening element feeding direction 891.

[0133] The connecting section 803 comprises a delay unit 819 and a delay unit check valve 899. The connecting section 803 is directly connected to the first chamber 801 with a first interface 835. Further, the connecting section 803 is directly connected to the spring compressing volume 815 of the second chamber 802. The connecting section 803 comprises a first connecting section 837 which is directly connected with the first chamber 801 and comprises a fluid communication with the first chamber 801. The connecting section 803 comprises further a second connecting section 839 which is directly connected with the second chamber 802 and comprises a fluid communication with the second chamber 802. A delay unit 809 is placed between the first connecting section 837 and the second connecting section 839 and comprises a fluid communication between the first connecting section 837 and the second connecting section 839.

[0134] Compared to the fastening tool 591 according to Figure 2, the fastening tool 800 comprises a connecting section 803, wherein said connecting section 803 further comprises a first check valve section 851 which is directly connected with the first chamber 801 and the first connecting section 837. The connecting section 803 further comprises a second check valve section 853 which is directly connected with the second chamber 802 and the second connecting section 839. A delay unit check valve 899 is placed between the first check valve section 851 and the second check valve section 853.

[0135] The working principle of the improvement of the state-of-the-art fastening tool 800 according to the invention can be described in four stages: Figure 8a shows how the first piston 809 moves in the driving direction 890. The pressure in the return volume 807 and the return chamber 811 are increasing due to the movement of the first piston 801. In Figure 8a the connecting section 803 is not directly connected with the return chamber 811. The connecting section 803 has a direct fluid communication either with the working volume 805 or with the return volume 807. In the case of Figure 8a the connecting section is neither connected with the working volume 805 nor with the return volume 807. (stage 1).

[0136] Figure 8b shows that the first piston 809 is forced to move in the driving direction 890 within the first chamber 801. The first piston 809 passed the first interface 835, and the working volume 805 is directly connected with the connecting section 803 (stage 2). This results in the same pressure within the working volume 805 and the connecting section 803 which leads to a first gas flow 841 in the first connecting section 837 and in the first check valve section 851. Due to the first gas flow 841 in the first check valve section 851 the check valve 899 is open and the first gas flow 841 enters the second chamber 802 through the second check valve section 853. The first gas flow 841 also enters the second chamber 802 through the delay unit 819 and the second connecting section 853.

[0137] In the meantime, the first piston 809 reaches the driving position and between the working volume 805 of the first chamber 801 and the spring compressing volume 815 of the second chamber 802 a pressure equilibrium is generated (stage 3, not shown). In other words: the first gas flow 841 is interrupted by the pressure equilibrium and at this stage no gas flow between the first chamber 801 and the second chamber 802 exists. In this stage the second piston 813 reaches the fully compressed position and the spring 833 within the fastening element feeding volume 817 is now fully compressed.

[0138] Figure 8c shows how the working pressure in the working volume 805 is released to the atmosphere and decreases the working pressure in the working volume 805. The pressure in the return volume 807 and in the return chamber 811 are now exceeding the working pressure in the working volume 805 and the first piston 809 is moved back form the driving position to the initial position. Since, the connecting section 803 is directly connected to the working volume 805 of the first chamber 801 a second gas flow 842 is generated from the spring compressing volume 815 of the second chamber 202 to the working volume 805 of the first chamber 801. (stage 4). The second gas flow 842 can only enter the first connecting section 803 through the delay unit 819. As a result, the spring 833 and the fastening element volume 817 are expanding and the second piston 813 is starting to direct the next fastening element 823 towards the first piston 809.

[0139] Figure 8d shows how the first piston 809 passes the first interface 835. The first connecting section 837 is now in fluid communication with the return volume 807 of the first chamber 801. Hence, the second chamber 802 now directly supports the return volume 807 and the return chamber 811 in returning the first piston 809 to the initial position. Since the second gas flow 842 is much weaker than the first gas flow 841, the feeding of the next fastening element 823 to the first piston 809 is significantly delayed. Hence a friction between the first piston 809 and the next fastening element 823 is avoided.

Claims

1. A fastening tool (591) for driving a fastening element (221) in a driving direction (290) into a workpiece, comprising - a first chamber (201), wherein the first chamber (201) comprising - a first piston (209) dividing the first chamber (201) into a working volume (205) and a return volume (207), - a second chamber (202), wherein the second chamber (202) comprising - a second piston (213) dividing the second chamber (202) into a spring compressing volume (215) and a fastening element feeding volume (217), - a connecting section (203) located between the first chamber (201) and the second chamber (202), wherein the connecting section (203) comprising: - a first connecting section (237) connecting the connecting section (203) with the first chamber (201), - a second connecting section (239) connecting the connecting section (203) with the second chamber (202), - a delay unit (219) connecting the first connecting section (237) with the second connecting section (239).

2. The fastening tool (591) according to the previous claim, wherein the delay unit (219) is configured to allow - a first gas flow (241) from the first chamber (201) to the second chamber (202) and - a second gas flow (242) from the second chamber (202) to the first chamber (201).

3. The fastening tool (591) according to the previous claim, wherein the delay unit (219) is configured to allow - the first gas flow (241) from the first chamber (201) to the second chamber (202) if a working pressure in the working volume (205) is greater than a return pressure in the return volume (207) and - the second gas flow (242) from the second chamber (202) to the first chamber (201) if a working pressure in the working volume (205) is less than a return pressure in the return volume (207).

4. The fastening tool (591) according to the previous claims 2 and 3, wherein the delay unit (219) is configured to allow - the first gas flow (241) from the first chamber (201) to the second chamber (202) if a fastening element feeding pressure in the fastening element feeding volume (217) is less than a spring compressing pressure in the spring compressing volume (215) and - the second gas flow (242) from the second chamber (202) to the first chamber (201) if a fastening element feeding pressure in the fastening element feeding volume (217) is higher than a spring compressing pressure in the spring compressing volume (215).

5. The fastening tool (591) according to the previous claims, wherein the delay unit (219) comprising - a hollow space, - a throttle element (40) placed in the hollow space.

6. The fastening tool (591) according to the previous claim, wherein the throttle element (40) comprising a first state and a second state.

7. The fastening tool (591) according to the previous claim, wherein the throttle element (40) further comprising an intersection opening, wherein said intersection opening of the first state of the throttle element (40) is greater than the intersection opening of the second state of the throttle element (40).

8. The fastening tool (591) according to the previous claims 6 and 7, wherein the throttle element (40) further comprising a trimmed section (43) allowing the intersection opening to change from the first state to the second state or to change from the second state to the first state.

9. The fastening tool (591) according to the previous claim, wherein the intersection opening is surrounded by the trimmed section (43) and the trimmed section (43) is a circle cutout.

10. The fastening tool (591) according to the previous claim, wherein the circle cutout comprising a circle cutout center and the intersection opening is placed in the circle cutout center.

11. The fastening tool (591) according to claims 5 to 10, wherein the throttle element (40) comprising a foldable section.

12. The fastening tool (591) according to claims 8 to 11, wherein the throttle element (40) comprising a throttle element center and the circle cutout center is placed in the throttle element center.

13. Method for delaying a fastening element feeding in a fastening tool (591) comprising the steps of: - providing a fastening tool (591) for driving a fastening element (221) in a driving direction (290) into a workpiece, wherein the fastening tool (591) comprising - a first chamber (201), wherein the first chamber (201) comprising - a first piston dividing the first chamber (201) into a working volume (205) and a return volume (207), - a second chamber (202), wherein the second chamber (202) comprising - a second piston (213) dividing the second chamber (202) into a spring compressing volume (215) and a fastening element feeding volume (217), - a connecting section (203) located between the first chamber (201) and the second chamber (202), wherein the connecting section (203) comprising: - a first connecting section (237) connecting the connecting section (203) with the first chamber (201), - a second connecting section (239) connecting the connecting section (203) with the second chamber (202), - a delay unit (219) connecting the first connecting section (237) with the second connecting section (239) and comprising a hollow space and a throttle element (40) placed in the hollow space, wherein said throttle element (40) comprising a first state and a second state, - generating a first gas flow (241) from the first chamber (201) to the second chamber (202), - changing the throttle element (40) from the second state to the first state.

14. Method according to the previous claim comprising the further steps of: - reaching a pressure balance between the first chamber (201) and the second chamber (202), - changing the intersection opening from the first state to the second state.

15. Method according to the two previous claims comprising the further steps of: - generating a second gas flow (242) from the second chamber (202) to the first chamber (201).

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