SAFETY VALVE FOR A PNEUMATICALLY OPERATED TOOL

Description

[0001] The invention relates to a pneumatically actuated tool according to the preamble of claim 1.

[0002] From EP 1163979 A1 a device for pneumatically actuating a tool and a pneumatic pliers are known.

[0003] Pneumatic pliers for crimping and clamping clamp rings, bolts, cable lugs, clamps, etc. are well known. Pneumatic pliers are particularly used in the automotive industry, where they are used to clamp clamp rings when assembling hoses, bellows, etc. to nozzles, drive shafts, and the like.

[0004] DE 15 03 020 A1 discloses a pneumatic tool according to the preamble of claim 1. DE 37 42 782 A discloses a pressure-operated pliers for spring band clamps with a valve-controlled pressure-operated connection and a wedge-shaped feed element. Further pliers of this type are known from documents DE 89 00 250 U, DE 195 19 543 A, DE 295 09 976 U, US 2004 / 031839, and DE 91 11 366 U.

[0005] In state-of-the-art tools, a pressure cylinder is pressurized by actuating a trigger unit. In some cases, the tool or a pressure supply includes an electronic control unit, which, due to a malfunction, could unexpectedly apply pressure to the trigger unit and close the tool. State-of-the-art tools lack any mechanical safety devices that could interrupt the energy supply (compressed air). If pressure is unexpectedly applied to the trigger unit, for example, due to a software error, the pliers or their jaws close. This can lead to dangerous situations. Therefore, various standards ensure that this unexpected closure is avoided.Since firmware with a simple structure is never considered completely safe according to common standards, the trip unit must be designed redundantly; in particular, this is achieved with an electronically redundant control unit.

[0006] The invention is particularly based on the object of providing an alternative to the electronically redundant design of the trigger unit and effectively preventing the tool from causing damage in the event of unexpected pressure build-up.

[0007] The object is achieved by a pneumatic tool having the features of claim 1. Advantageous embodiments of the invention emerge from the subclaims.

[0008] The invention relates to a pneumatic tool, in particular an electronically controlled pneumatic tool in which the applied pressure is electronically monitored. The tool comprises a handle, a safety switch lever arranged on the handle for actuating a valve, and a pressure medium connection. The valve comprises a valve body movable between a basic position and at least one further position. In the basic position, a connection between the pressure medium connection and a pressure cylinder of the tool is interrupted, and in the further position, the connection between the pressure medium connection and the pressure cylinder of the tool is established.

[0009] The tool may in particular be a pair of pliers, but it is also conceivable that the invention could be used in other tools.

[0010] It is proposed that the pressure cylinder be vented when the valve body is moved to its home position, and that a pressure applied to the pressure medium connection moves the valve body to its home position when the safety lever is released. The effect of the pressure safely returns the valve to its home position without manual intervention when the user releases the safety lever, for example, due to an injury. At the same time, the pressure cylinder is vented, allowing any trapped elements such as fingers or clothing to be safely removed.

[0011] According to the invention, the valve body is designed as a sleeve that can be displaced on a pressure supply connection piece, the inner surface of which, together with an outer surface of the pressure supply connection piece, encloses a pressure chamber. The two axial end faces of the pressure chamber are formed by inner surfaces of the sleeve and have different surface areas or pressure application surfaces. This allows the desired functionality to be achieved with a robust and compact design.

[0012] The different pressure application surfaces can be implemented particularly easily if the outer diameter of the pressure supply connection piece on the side open toward the pressure cylinder is larger than the outer diameter of the pressure supply connection piece on the side open toward the pressure medium connection. In the case of an axially movable sleeve, the axial projections of the inner end faces of the sleeve correspond to the pressure application surfaces.

[0013] In a preferred embodiment of the invention, the pressure supply connection piece can in particular comprise a first inner bore open towards the pressure medium connection and a second inner bore open towards the pressure cylinder, as well as first and second, in particular radial, pressure passage bores, the latter connecting the first and second inner bores, respectively, to the outer surface of the pressure supply connection piece. In the basic position, the first passage bores open into the pressure chamber, and the second passage bores are open for venting. This vents the pressure cylinder in the basic position. In the further position, the first and second passage bores open into the pressure chamber, so that the pressure from the pressure medium connection is passed through the first pressure passage bores into the pressure chamber, from there through the second pressure passage bores into the second inner bore, and thus to the pressure cylinder.

[0014] In a further embodiment, the tool further comprises a spring that generates a return force that moves the valve body to its home position when the safety lever is released. The spring can support the pressure during the return of the valve body, so that even at low pressures (or even no pressure in the system), the valve is transferred to the safe, closed home position. The spring can be designed such that a frictional force of the valve body can always be reliably overcome, thus creating further redundancy of the safety valve.

[0015] In other words, the invention proposes providing a 3 / 2-way safety valve directly in the trigger unit of the tool according to the invention, thus preventing the tool or pliers from closing in the event of an unexpected pressure buildup, which could potentially injure people. The safety valve only releases the pressure passage when necessary.

[0016] It is also proposed that the safety valve be operated purely mechanically. This has several advantages, in particular that no additional electronics are required, the very tight installation space is not overloaded, and the grip force required to hold the trigger unit in place can be utilized.

[0017] The invention ensures that the compressed air supply is always interrupted when the safety lever is not pressed. This corresponds to the safe home position. At the same time, the tool's pressure cylinder is safely vented in the home position. If the safety lever is now pressed, the safety valve is positioned so that the vent is closed and pressure can flow unhindered into the pliers. The safety valve is designed to return to the safe pressure position without actuation, so that the tool is automatically locked and vented.

[0018] Further features and advantages will become apparent from the following description of the figures. The entire description and the figures disclose features of the invention in specific embodiments and combinations. Those skilled in the art will also consider the features individually and combine them into further combinations or subcombinations to adapt the invention, as defined in the claims, to their needs or specific areas of application.

[0019] Showing: Fig. 1 a pneumatic tool designed as pliers according to a first embodiment of the invention; Fig. 2 a valve of the tool Fig. 1 in a basic position; Fig. 3 the valve Fig. 2 in another position; Fig. 4a and 4b the valve from the Figures 2 and 3 in a larger context; Fig. 5a and 5b a first longitudinal section of a handle of a pneumatic tool according to the invention; and Fig. 6a and 6ba second longitudinal section of a handle of a pneumatic tool according to the invention.

[0020] Figure 1 shows a pneumatic tool 10 designed as pliers according to a first embodiment of the invention.

[0021] The pliers are designed for installing pipe clamps, hose clamps, clamping rings, etc. Several pistons 14 arranged in series or one behind the other are arranged in a pressure cylinder 12.

[0022] At the rear end of the manually operable pneumatic pliers, a pressure medium connection 16 is provided, by means of which the pliers can be connected to a pressure medium, such as compressed air, via a pressure line (not shown), wherein the pressure medium supply can be opened or the tool 10 can be vented by means of a safety switch lever 18, which actuates a valve 22.

[0023] The individual pistons 14 have a passage through the piston rods to allow pressure fluid to pass through. Radially outward-facing outlet openings are provided near the front end of the piston rods. Compressed air can exit through these outlet openings. The compressed air drives the next piston 14 forward. The passage of compressed air through the passage of the next piston rod is repeated in a similar manner.

[0024] In the direction of the pliers tool 20, on the frontmost piston 14, follows the so-called wedge piston 24, on the front of which a wedge-shaped feed member is arranged for actuating the pliers head or pliers tool 20. The wedge piston 24, driven forward by the pressure medium, forces the two pliers jaws of the pliers tool 20, which are mounted on bolts, for example, apart in the rear area by sliding the wedge surface between two rollers. At the same time, the two pliers jaws of the pliers tool 20 are forced together at the front in the closing direction, for example, to clamp a hose clamp or to press ear clamps or the like by actuating the pliers tool 20.

[0025] The pneumatic tool further comprises a handle 26, on which the safety switch lever 18 for actuating the valve 22 is arranged. Furthermore, a circuit board with an electronic switching unit 38 is provided in the handle 26, which outputs a pressure request signal to the pressure source via the signal line in the pressure line.

[0026] Fig. 2 shows the valve 22 in the basic position, in which a connection between the pressure medium connection 16 and a pressure cylinder 12 of the tool 10 is interrupted. The valve 22 comprises a valve body 28 designed as a sleeve, which can be moved between the basic position and at least one further position ( Fig. 3 ) is movably arranged on a pressure supply connection piece 30.

[0027] The pressure supply connection piece 30 has a first inner bore 30a open towards the pressure medium connection 16 and a second inner bore 30b open towards the pressure cylinder 12, as well as first and second radial pressure passage bores 32a, 32b. The pressure passage bores 32a, 32b connect the first or second inner bore 30a, 30b with the outer surface of the pressure supply connection piece 30. In the Fig. 2 In the basic position shown, the first pressure passage holes 32a open into a pressure chamber 34 of the valve 22 and the second pressure passage holes 32b are released for venting.

[0028] By moving the valve body 28 into the basic position, the pressure cylinder 12 can therefore be vented via the second pressure passage bores 32b.

[0029] The inner surface of the valve body 28, which is designed as a sleeve and is displaceable on the pressure supply connection piece 30, encloses the pressure chamber 34 with an outer surface of the pressure supply connection piece 30, wherein the two axial end faces 34a, 34b of the pressure chamber 34 are formed by inner surfaces of the sleeve and have different surface areas. The different surface areas result in different pressure forces acting in opposite directions and a resulting force acting in the direction of the end face 34b with the larger surface area, i.e. Fig. 2 and 3 to the right, and displaces the valve body 28 towards the home position. Therefore, a pressure applied to the pressure medium connection 16 displaces the valve body 28 in the orientation according to Fig. 2 and 3to the right into the basic position without the user or any other force having to be exerted on the valve body 28.

[0030] Sealing rings 36 are provided on the inner edges of the end faces 30a, 30b of the valve body 28, which face the outer surfaces of the pressure supply connection piece 30, to seal the pressure chamber 34. In particular, the use of lip seals with an X-profile, i.e., X-rings or quad rings, has the advantage of low static friction and dynamic friction.

[0031] The valve 22 is therefore safely moved into the basic position ( Fig. 2 ) when the user releases the safety lever 18, for example, because of an injury. At the same time, the pressure cylinder 12 is vented so that any trapped elements such as fingers, clothing, or the like can be easily and safely removed.

[0032] The different areas are achieved by different outer diameters of the pressure supply connection piece 30, namely by the fact that the outer diameter of the pressure supply connection piece 30 on a side open toward the pressure cylinder 12 is larger than an outer diameter of the pressure supply connection piece 30 on a side open toward the pressure medium connection 16. The areas with different outer diameters are separated by a step that is bridged by the sleeve of the valve body 28.

[0033] Fig. 3 shows the valve 22 in the further position, in which the connection between the pressure medium connection 16 and the pressure cylinder 12 of the tool is established. In the further position, both the first and second passage bores 32a, 32b open into the pressure chamber 34. This establishes a pressure connection from the pressure medium connection 16 via the pressure chamber 34 to the pressure cylinder 12.

[0034] By operating the safety switch lever 18, the valve 22 is actuated and thus opened or switched to the configuration of the Fig. 3 moved, whereby the valve body 28 designed as a sleeve in the view according to Fig. 3 is pushed to the left. By holding the safety lever 18, the valve 22 is kept open ( Fig. 3 ). If the safety lever 18 is now released, e.g. due to a trapped finger, the valve 22 closes automatically due to the continued pressure ( Fig. 2 ).

[0035] The resulting force used for closing arises because the pressurized surfaces are not identical. In the direction of the home position, the annular area is larger, resulting in a resulting self-closing force. This ensures that valve 22 always closes under pressure.

[0036] When pressure is applied, valve 22 is therefore not bistable like regular 3 / 2 valves but monostable.

[0037] Fig. 4a and 4b show the valve from the Figures 2 and 3 in a larger context. In the example from Fig. 4a and 4b A spring 36 is provided, which generates a restoring force that moves the valve body 28 into the home position when the safety switch lever 18 is released and acts in the same direction as the force resulting from the pressure forces. The spring 36 therefore supports the pressure forces when resetting the valve body 28 in such a way that even at low pressures or without any pressure at all, the valve 22 is transferred to the safe, closed home position. However, embodiments without the additional spring 36 are also conceivable.

[0038] The pressure supply connection piece 30 is inserted into an adapter piece 40 for connecting a pressure supply hose (with integrated signal line). An axially forward end of the adapter piece 40 forms a stop for the valve body 28. An O-ring 42 is provided there to dampen the stop.

[0039] Fig. 5a and 5b show a first longitudinal partial section of the handle 26 of the pneumatic tool according to the invention. The valve body 28 is provided with a bevel 44, on which a projection 46 connected to the safety switch lever 18 slides with a corresponding bevel. The safety switch lever 18 is pivotally connected to the handle 26 via a joint arranged at the rear end of the handle 26.

[0040] By grasping the handle 26 with one hand, the user pivots the safety switch lever 18 from a closed position ( Fig. 5a ) inwards into an open position ( Fig. 5b) and the valve body 28 is pushed over the projection 46 and the bevel 44 into the open position.

[0041] Fig. 6a and 6bis a second partial longitudinal section of the handle 26 of the pneumatic tool according to the invention. An angular switching extension 48 attached to the valve body 28 actuates a safety switch 50 arranged in the handle 26, which must be closed so that the electronic switching unit 38 arranged in the handle 26 outputs a pressure request signal to the pressure source via the signal line in the pressure line. When the switching body 28 is moved into the open position, the safety switch 50 is actuated via the switching extension 48 and a contact in the safety switch is closed, thus fulfilling a necessary condition implemented in the logic of the electronic switching unit 38 for triggering the pressure request signal. The switching extension 48 therefore establishes a mechanical connection between the valve body 28 and the electromechanical safety switch 50, which allows the electronic switching unit 38 to monitor the valve 22. List of reference symbols

[0042] 10Tool 12Pressure cylinder 14Piston 16Pressure medium connection 18Safety switch lever 20Plier tool 22Valve 24Wedge piston 26Handle 28Valve body 30Connection piece 32a, 32bPressure passage holes 34Pressure chamber 36Spring 38Switching unit 40Adapter piece 42O-ring 44Bevel 46Protrusion 48Switching extension 50Safety switch

Claims

1. A pneumatic tool with a handle (26), a valve (22), a safety lever (18) arranged on the handle (26) for actuating the valve (22) and a pressure medium connection (16), wherein the valve (22) comprises a valve body (28) movable between a basic position and at least one further position, wherein in the basic position a connection between the pressure medium connection (16) and a pressure cylinder (12) of the tool is interrupted and in the further position the connection between the pressure medium connection (16) and the pressure cylinder (12) of the tool is established, wherein the pressure cylinder (12) is vented with the shifting of the valve body (28) into the basic position and a pressure applied at the pressure medium connection (16) shifts the valve body (28) into the basic position when the safety lever (18) is released, characterized in that the valve body (28) is a sleeve displaceable on a pressure supply connecting socket (30), the inner surface of which encloses a pressure chamber (34) with an outer surface of the pressure supply connecting socket (30), wherein the two axial end faces (34a, 34b) of the pressure chamber (34) are formed by inner surfaces of the sleeve and have different surface areas.

2. A pneumatic tool according to claim 1, characterized in that an outer diameter of the pressure supply connecting socket (30) on a side opened towards the pressure cylinder (12) is larger than an outer diameter of the pressure supply connecting socket (30) on a side opened towards the pressure medium connection (16).

3. A pneumatic tool according to one of the preceding claims, characterized in that the pressure supply connecting socket (30) comprises a first inner bore (30a) opened towards the pressure medium connection (16) and a second inner bore (30b) opened towards the pressure cylinder (12) as well as first and second pressure passage bores (32a, 32b), which connect the first or second inner bore (30a, 30b) with the outer surface of the pressure supply connecting socket (30), wherein in the basic position the first pressure passage bores open into the pressure chamber (34) and the second pressure passage bores (32b) are released for venting and in the further position the first and the second pressure passage bores (32a, 32b) open into the pressure chamber (34).

4. A pneumatic tool according to one of the preceding claims, characterized by a spring (36) that generates a return force which shifts the valve body (28) into the basic position when the safety lever (18) is released.

5. A pneumatic tool according to one of the preceding claims, characterized by an electrical or electronic control unit (38) with an electromechanical safety switch (50) that is mechanically connected to the valve body (28).