EP0297156A1 - Pneumatically operated fastener driving tool - Google Patents

Abstract

1. A pneumatically operated driving tool for fasteners comprising a working cylinder, a working piston within said working cylinder connected to a driver or the like, stop means in said working cylinder limiting the working stroke of said working piston, a control valve adapted to be actuated by a trigger, a working space above said working piston when said piston is in its upper dead point position, said control valve being adapted to alternatingly connecting said working space with a pressurized air source or with atmosphere, respectively, a piston return chamber surrounding said working cylinder and connected thereto by a first opening adjacent said stop means, and a second opening spaced from said stop means, characterized by said working piston having a smaller diameter than said working cylinder, an annular piston being sealingly displaceable on said driver and sealingly engaging the wall of said working cylinder, said annular piston sealingly engaging said working piston in said upper dead point position, the proportion of the effective areas and the masses of said working piston and said driver blade on one side and of said annular piston on the other side being such that the acceleration of said annular piston during the working stroke is not larger than that of the working piston.

Description

The invention relates to a pneumatically operated fastening device for fastening means according to the preamble of patent claim 1.

Pneumatically actuated driving tools for driving nails, staples, pins, sleeves or the like of different lengths and other dimensions are generally known. They have a driving plunger which is driven by a piston, which in turn is sealingly guided in an air cylinder. A space above the working piston in its top dead center position is optionally connected to a compressed air source or to the atmosphere with the help of a control valve. The fasteners are usually strip-shaped magazi niert and are advanced with the aid of a suitable feed device in the direction of a shot channel through which the driving plunger strikes the fastener into a workpiece.

It is also known to design the control valve so that a sequence of driving strokes is triggered as long as an operating lever or the like is operated. With the aid of such a repeating valve, a relatively high number of impacts per unit of time can be achieved, so that, for example, U-clamps can be driven into a workpiece in rapid succession. The repeating valve is a relief for the operator. They do not have to release the trigger with every driving stroke and actuate it again for a further driving stroke.

After completing a working stroke, the working piston must be moved back to its starting position. It is known to provide a spring for returning the piston. However, a spring has several disadvantages. It can tire and break after a certain operating time. Furthermore, the spring requires a relatively large amount of additional energy for its deformation over an inevitably long spring travel. Furthermore, the deformation work of the spring also creates friction, which consequently leads to energy losses.

It is therefore more common to pneumatically effect piston return. For this purpose, the working cylinder is surrounded by a return chamber which is connected to the cylinder via at least two openings. One opening is very close to the stop of the working piston, while the other opening is so far away from the stop that it lies above the working surface of the working piston when it hits the stop. In this way, the compressed air passes through the upper opening into the return chamber and pushes the piston back up through the lower opening to the starting position.

Such a pneumatic piston return means that the fastening means is driven into the workpiece almost or entirely with a driving impact. If this is not the case, there is at most a certain return effect due to the piston impact if the fastener gets stuck. At the next drive-in stroke, there is only a very small piston travel available to drive the fastener a little further. Therefore, drive-in devices are normally dimensioned such that a single drive-in stroke will certainly result in the fastener being driven in completely, even if relatively hard workpiece material is being processed. The size and weight are therefore measured determined primarily by the energy required to drive in a fastener with just one stroke. If relatively thick and long nails are to be driven in, the driving tools required for this are relatively heavy and unwieldy. Furthermore, large driving tools are often not usable in confined spaces.

Another disadvantage of known driving tools, especially for nails in connection with beam plates, is that the high energy can lead to the nail head tearing off the shaft, due to the extremely strong delay when the nail head hits the top of the beam plate. Furthermore, in spite of trigger safeguards in the case of such devices, there is a considerable risk of injury if the nail strikes the beam plate when inadvertently moved.

Despite the corresponding design, it is not always possible with so-called single-shot nailers to get evenly driven in nails without manual looking up.

The invention has for its object to provide a pneumatically operated fastener driving device that allows pneumatic piston return even with only partially driven fastener.

This object is achieved by the features of the characterizing part of claim 1.

In the driving tool according to the invention, an annular piston is arranged below the working piston. It is either a simple screw that sealingly interacts with the lower surface of the working piston; or it has an axial flange which laterally engages around the working piston. In the latter case, the sealing can also take place laterally between the working piston and the annular piston flange. The ring piston works in a sealing manner with the driving plunger and the working piston. However, it can be moved relative to the working piston. It is also essential to the invention that the mass and the effective area of the annular piston in relation to the mass of the working piston and plunger and the effective area of the working piston are dimensioned such that the annular piston is advanced together with the working piston when a pressure build-up takes place above the working piston via the control valve. The annular piston does not contribute to driving in the fastener during its downward movement with the working piston. If the fastener is only partially driven in, the kinetic energy of the driving plunger and the piston is used up. The suddenly occurring delay of the driving plunger, however, leads to the ring piston becoming detached from the working piston. From a certain relative displacement of the working piston and the annular piston, the originally relatively small effective area of the annular piston increases. The ring piston can therefore be moved towards the stop (brake ring) with acceleration. Arrived at the stop piston retrieval takes place according to the principle described above. Since the diameter of the working piston is smaller than the inside diameter of the working cylinder, compressed air can enter the piston return chamber. The return of the ring piston also takes the working piston to the top dead center position as soon as the ring piston engages the working piston from below. The ring piston is therefore an aid to pneumatically return the working piston from any position between the top and bottom dead center to the top dead center. The piston return according to the invention therefore enables the design of a conventional pneumatic single-use driving device to be a multi-impact driving device, the number of strokes being determined by the actuation time of the trigger and the stroke frequency by the corresponding design of the control valve.

There can therefore be several driving strokes in the unchanged position of the device on the fastening means to be driven in, in order to drive the fastening means completely with low energy of the individual impact.

Since in the multi-impact driving device according to the invention the working piston is moved back to the starting position before each driving impact, its kinetic driving energy increases to the same extent as with the further driven fastener means the lead per stroke increases. The effective driving energy of the ram therefore increases with increasing driving resistance of the fastening means.

The driving tool according to the invention has considerable advantages. The operator actuates the driving tool until he feels or hears that the nail head rests on the workpiece. Based on experience, the operator can also adequately measure the driving process for each nail. It is therefore possible to drive in nails or other fasteners evenly.

In the driving tool according to the invention, the driving energy per shot can be chosen to be much smaller than in impact devices. The driving tool according to the invention can therefore be significantly reduced in size and weight compared to known devices. It is therefore easier to handle and can also be used advantageously in tight spaces. Smaller driving tools naturally also require less material and manufacturing costs.

The higher the driving energy for impact driving tools, the greater the risk to the operator if there is a false trigger or a drop bounce off a nail, for example on a metal sheet. In the driving tool according to the invention, the driving energy per driving stroke is much lower, so that there is also a lower safety risk.

Finally, the fastener is less loaded when processing with the driving tool according to the invention than with impact driving tools. It eliminates the risk of cracking between the head and shaft of a nail.

The driving tool according to the invention is equally suitable for driving in magazine and individual fasteners.

The fasteners are usually lined up in strips so that they can be stored in a suitable manner. Staples are processed into staple rods, nails into nail strips, which are held together with the help of plastic bands or the like. In this context it is also known to provide a suitable feed device in order to advance the next one into the firing channel after driving in a fastening means. With U-shaped clamps, a spring-loaded feeder is often sufficient. Pneumatically operated nails are often used Feed device used. In the driving tool according to the invention, the feed of a nail strip or a nail winding (nail coil) can be controlled so that a nail only enters the firing channel before the start of a multiple-stroke driving process. This prevents false triggering or a nail being pushed in while another is still halfway in the firing channel. An additional trigger can be provided on the driving tool to actuate the feed device. According to the invention, an alternative possibility is to couple the actuation of the feed device with the release of the release lever. If the release lever is released after a driving-in process, the feed device is activated and pushes a new fastening means into the firing channel.

It is known in the case of driving tools to assign a mechanical sensor to the mouth of the firing channel, which sensor is actuated when the driving device is placed on a workpiece. The sensor controls the control valve or the release valve mechanically or pneumatically and has the effect that a shot is only triggered if the sensor is actuated at the same time. In the driving tool according to the invention, such a sensor can also be used to accomplish the nail advance. About the sensor is mecha nisch or pneumatically controlled the feed direction.

If the fastening means are bound to one another, for example by gluing or by other connecting means, the connection is sheared off by the driving plunger. However, the last fastening means, for example a nail, is no longer held by the following one. Rather, there is a risk that it will slide out through the firing channel.

Therefore, an embodiment of the invention provides that the shot channel in the area in which the head of the nail emerges from the magazine has at least one holding jaw which is biased radially inwards by at least one spring to hold the nail in the shot channel before driving . The holding jaw can additionally or alternatively be magnetic in order to hold a nail in the firing channel.

• Fig. 1 zeigt einen Schnitt durch ein Eintreibgerät nach der Erfindung.
• Fig. 2 zeigt eine Ansicht des Eintreibgeräts nach Fig. 1 in Richtung des Pfeils 2, wobei jedoch nur ein kleiner Abschnitt gezeigt ist.
• Fig. 3 zeigt einen Schnitt durch die Darstellung nach Fig. 1 entlang der Linie 3-3.
• Fig. 4 zeigt einen Schnit eines Eintreibgerätes in einer anderen Ausführung mit Kopfventilsystem.

The invention is explained in more detail below with reference to drawings.

• Fig. 1 shows a section through a driving tool according to the invention.
• FIG. 2 shows a view of the driving device according to FIG. 1 in the direction of arrow 2, but only a small section is shown.
• Fig. 3 shows a section through the representation of FIG. 1 along the line 3-3.
• Fig. 4 shows a section of a driving tool in another embodiment with a head valve system.

Before going into the details shown in the drawings, it should be stated that each of the features described is of importance for the invention, either individually or in conjunction with features of the claims.

The driving tool shown in Fig. 1 consists of a cylinder part 10, a muzzle tool 11 attached under the cylinder part 10, a handle part 12 which is attached to the cylinder part 10, and a magazine 13 which is arranged between the muzzle tool 11 and an extension of the handle part 12 is.

ist.
wobei A1 die Wirkfläche des Arbeitskolbens 23, A2 die Wirkfläche des oberen Abschnitts des Ringkolbens 26, m1 die Masse von Arbeitskolben 23 und Stößel 24 und m2 die Masse des Ringkolbens 26 ist.Auf die Funktion der beschriebenen Teile wird weiter unten eingegangen.The cylinder part 10 has a cylindrical housing 14, which consists of two sleeves arranged one inside the other, and is sealed off in the upper region by a cap 16. A working cylinder 17 is arranged in the housing 14. It has an outer radial collar 18 which cooperates in a sealing manner with the inner wall of the housing 14. This forms an upper chamber 19 and a lower chamber 20. The lower chamber 20 is connected to the interior of the cylinder via lower openings 21 and via upper openings 22. A working piston 23 is arranged in the cylinder, the diameter of which is smaller than the inside diameter D2 of the working cylinder. A cylindrical tappet 24 is connected to the working piston 23 and extends through an opening of a brake ring 25 at the lower end of the cylinder 17. The working cylinder 23 is surrounded by a cup-shaped annular piston 26. A relatively thin cylindrical section of the annular piston 26 interacts with a seal 27 of the piston. A section of the annular piston 26 with a smaller inside diameter cooperates with the driving plunger 24 by means of a seal 29. An annular seal 28 on the outside of the annular piston 26 interacts in a sealing manner with the cylinder wall. The inner diameter of the active surface of the upper section of the annular piston 26 is denoted by D1, while the diameter of the tappet is D3. The mass of piston 23 and tappet 24 on the one hand and of the annular piston 26 on the other hand and the diameter of the active surfaces of the two pistons is selected such that

is.
where A1 is the effective area of the working piston 23, A2 is the effective area of the upper section of the annular piston 26, m1 is the mass of the working piston 23 and plunger 24 and m2 is the mass of the annular piston 26. The function of the parts described will be discussed below.

A weft channel 30 is provided in the mouthpiece 11, each of which receives an annular shaft nail 31 of a nail strip 32, the individual nails 31 being held together by, for example, plastic strips 33. They are guided in magazine 13 in a known manner. A feed device, not shown, is used to feed the strip 32 in the direction of the firing channel 30. A sensor 34 is also assigned to the muzzle tool 11, the function of which will be described later.

In the handle part 12 there is a reservoir 35 which is connected to a connection 36 for connection to a compressed air line in a manner known per se. A release lever 37 is pivotally mounted on the underside of the handle part. It actuates a release valve 38, which in turn interacts with a repeating control valve 39. The repeating valve 39 is connected to the annular space 19 via a bore 40. The annular space 19 is over a plurality of bores 41 connected to a space 42 above the working piston 23 in its top dead center position or below the plug 16.

The described driving-in device works as follows: The preferably pneumatically operating feed device, not shown, has advanced the strip 32 so far that an annular shaft nail 31 is located in the weft channel 30. This process takes place after an annular shaft nail 31 has been driven into the beam 45 via a hole 43 in a sheet metal 44 on a beam 45. If the trigger lever 37 is now actuated, the control valve 39 ensures that the space 42 is connected to the compressed air reservoir 35. The working piston 23 then starts to move in a known manner. The ratio of the effective areas and the masses already mentioned is such that the annular piston 26 is never accelerated more strongly than the working piston 23. The working piston 23 therefore always pushes the annular piston 26 a little in front of itself. However, the driving energy is designed such that normally the nails 31 are not driven into the workpiece 45 in one stroke.

There is therefore no risk of injury if the nail accidentally hits the beam plate.

Rather, the nail 31 is driven in only by a certain amount, the driving plunger 24 and thus the piston 23 being decelerated relatively quickly and finally being stopped. The kinetic energy inherent in the annular piston 26 causes the annular piston 26 to continue on its way. If the upper section of the annular piston disengages from the seal 19 of the piston 23, its effective area exposed to the driving pressure increases, as a result of which the annular piston 26 moves downward with greater acceleration. At the moment when its upper side has passed through the openings 22, the compressed air can enter the return chamber 20 via the openings 22 and pressurize the annular piston 26 from below via the bore 21. In this way, the annular piston 26 is pneumatically retrieved (in the known manner in accordance with the pneumatic piston retrieval in known driving tools). On the return stroke, the annular piston 26 takes the working piston 23 with it and conveys it to the top dead center position.

The control valve 39 is a repeating valve, ie relief or venting of the pressure chamber 42 is followed by a renewed pressurization. The control valve 39 can therefore apply any number of pressure surges to the work cause piston 23, this number depends only on how long the trigger lever 37 is operated. If the working piston 23 has therefore reached its top dead center position, the control valve 39 effects a further driving stroke. The driving tool shown is therefore a multi-impact device. The operator will therefore operate the release lever 37 until he sees or feels that the nail has been fully driven. It should be mentioned that the control valve is of a type known per se. Its function is therefore not discussed in detail here.

4 shows a further customary embodiment of a repeating valve as a so-called head valve system 60. It can also serve for the pneumatic control of the compressed air supply to the piston arrangement 23, 26. This repeating valve is also actuated indirectly by a trigger lever 61 via a known trigger valve 62. When the repeating valve is triggered, this, like in the valve arrangement already described, alternately pressurizes and depressurises the pressure space above the piston arrangement 23, 26.

In Fig. 2 it can be seen that the L-shaped sensor plate 34 axially displaces on the outside of the mouthpiece 11 bar is mounted, the limitation being carried out with the aid of a pin 50 which is seated in an elongated hole 51 in the plate 34. The cross leg of the plate 34 cooperates with a spring 52 and an adjusting rod 53. It serves to act either mechanically directly on the actuating valve 38 or the control valve 39 or on the pneumatic feed (not shown) for the nail strip 32. The control with the aid of the sensor 34 can be such that the feed device advances the nail strip 32 by a nail spacing width and conveys a new nail into the firing channel 30 when the sensor 34 is moved upward by placing it on a workpiece. This also ensures that accidental triggering of the working piston 23 does not lead to the imposition of a nail, which could endanger the operator or other persons. However, the sensor 34 can also bring about an additional safety function in that a release using the release lever 37 is not possible. It goes without saying that the feed device can also be controlled in a different way, for example via the release lever 37. The feed of a nail can take place, for example, at the moment in which the operator releases the trigger 37 after a multiple-stroke actuation. As can be clearly seen from FIG. 1, the nail advanced into the firing channel 30 is held in position by the holding strip 33. Therefore, it cannot slide out undesirably. This possibility of stopping does not exist for the last nail of a strip. From Fig. 3 it can be seen that in an axial region of the upper part of the firing channel 30, a plurality of jaws 55 limit the firing channel 30.

The jaws diverge upwards, so that in the event of an accidental triggering the plunger 24 does not strike the jaws 55 from above, if there is no nail in the firing channel 30 and the jaws 55 are at a minimum distance from one another in a relaxed position. When a nail 31 is advanced into the firing channel 30, its head is gripped by the jaws 55. In the event of a stroke, the driving plunger 24 hits the nail head and forces it out of the area of the jaws. The narrowest cross section between the jaws 55 is preferably dimensioned so that the driving plunger 24 can pass freely. The jaws 55 can also be magnetic to increase the holding effect of a nail 31.

Claims (9)

1. Pneumatically actuated fastener driving device with a working cylinder, in which a working piston holding a driving plunger is arranged and in which a stop limits the working stroke of the working piston, a control valve which can be actuated by a trigger and which during its actuation has a working space above the working piston in its upper Dead center position alternately connects to a compressed air source or atmosphere, and a piston return chamber surrounding the working cylinder, which is connected to the working cylinder via a first opening near the stop and a second opening at a distance from the stop, characterized in that the working piston (23) is smaller in diameter is as the diameter of the working cylinder (17), an annular piston 26 arranged sealingly in the working cylinder (17) and displaceable sealingly on the driving plunger (23) and in the top dead center position sealingly cooperates with the working piston (23), the ratio the effective surfaces and the masses of the working piston (23) and driving plunger (24) on the one hand and the annular piston (26) on the other hand is such that the annular piston (26) is not accelerated more than the working piston (23) during the working stroke. 2. Driving tool according to claim 1, characterized in that the driving plunger (24) is circular in cross section. 3. Driving tool according to claim 1 or 2, characterized in that the upper active surfaces of the two pistons (23, 26) are approximately at the same height. 4. Driving tool according to one of claims 1 to 3, in which a feed device is provided for feeding a strip of fastening means in the direction of the firing channel, characterized in that a fastening means (31) is pushed into the firing channel (30) shortly before triggering a driving stroke . 5. Driving tool according to claim 4, characterized in that the feed device is actuated by a separate trigger. 6. A driving tool according to claim 4, characterized in that the feed device is controlled by the trigger (37), preferably in such a way that a fastening means (31) in the firing channel (30) is advanced when the trigger (37) after actuation again is solved. 7. driving tool according to claim 4, in which the mouth (11) of the firing channel (30) is associated with a sensor (34) which is actuated when the driving device is placed on a workpiece (45), characterized in that the feed device from the sensor ( 34) is controlled. 8. Driving tool according to one of claims 1 to 7, characterized in that the firing channel (30) in the area in which the fastening means (31) enters from the magazine (30) has at least one holding jaw (55) which is of at least a spring (57) is biased radially inward to hold the fastener in the firing channel (30) before driving. 9. A driving tool according to claim 8, characterized in that the holding jaw (55) is magnetic.

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