Patent Application
20240173832
The present invention relates to handheld setting tools for driving or setting a nail or bolt.
Setting tools or nail setting tools which store the energy required for the setting operation in a pretensioned gas spring are generally known, for example, from WO 2009/046076 A1 and are marketed by Senco under the trade name “Fusion Technology”. Tools that work according to the same principle are also offered by HITACHI and are said to achieve driving energies or setting energies of 120 J.
Such nailers or nail setting tools (“pneumatic setting tools”) are well suited to driving or setting nails into wood, but they have a number of disadvantages compared to combustion-powered setting tools that severely limit their range of application.
For example, pneumatic setting tools do not appear to be well suited to driving or setting bolts into solid substrates such as steel or concrete, due on the one hand to low driving energy or setting energy and on the other hand to the possible recoil. The latter can be illustrated by the following edge case: A nail of length s is to be driven into a substrate, but the substrate and the nail do not yield at all. In this case, the substrate forms a counter bearing for the relaxing gas spring. The relaxation of the gas spring then accelerates the pneumatic gun over the distance s during the setting operation, whereupon the gas spring, with its force F, performs work w=∫(F*ds). With driving/setting energies such as those required for driving/setting into concrete and steel, this can soon lead to recoil energies with potentially disastrous results for the user. Recoil can also be a problem for electrodynamically driven setting tools.
Another deficiency of known pneumatic setting tools is their comparatively low driving energies and their relatively high weight and volume compared to combustion-powered setting tools with the same driving energy. This deficiency is essentially due to the comparatively low operating pressures of the devices. It is not without reason that WO 2009/046076 A1 expressly recommends low operating pressures between 100 psig and 120 psig, i.e. pressures corresponding to the usual operating pressures of pneumatic actuators: Enormous demands are made on the piston rings in pneumatic setting tools. They are supposed to keep the leakage-related pressure loss in the working gas reservoir, i.e. in the gas spring, at a negligible level over the entire service life of the setting tool, yet have to withstand extraordinarily high sliding velocities for pneumatic systems during the setting operation, and also cause minimal friction while sliding. If, for example, pressures of 1.2 kpsig were used instead of 120 psig, the contact pressures applied to the seals would have to be some ten times higher in order to achieve sealing, and the PV values of all piston seals commonly used in pneumatic applications would be far exceeded even at (for setting tools) moderate piston speeds of the order of 30 m/s. Therefore it is understandable that WO 2009/046076 A1 explicitly warns against operating pressures much higher than 120 psig.
In DE 10 2007 000 219B4, the company HILTI suggested solving the sealing problem by means of a rolling diaphragm; however, the service life of such a diaphragm appears doubtful given the enormous dynamic stress to which it is exposed in the setting tool.
A further disadvantage of known pneumatic setting tools is that it is difficult to adjust the driving energy, whereas this can easily be achieved with, for example, combustion-powered tools. For example, in a setting tool driven by the combustion of an ignitable gas-air mixture, the amount of fuel injected can be varied. In powder-actuated tools, cartridges can be loaded with a propellant charge adapted to the application.
Finally, another disadvantage of known setting tools that have a piston drive is that they have a pronounced muzzle flip and recoil, which can reduce setting quality and place physical strain on the user.
It is the object of the present invention to solve the problems referred to above.
These problems are solved by a handheld setting tool with the features according to claim 1. Preferred embodiments are defined in the dependent claims.
Further advantages and further embodiments of the invention will be apparent from the following detailed description and from the claims as a whole.
The invention is described below on the basis of further embodiments and examples, starting with known pneumatic and electrodynamically driven setting tools. The examples serve to provide a better understanding of the invention: in no way are they to be understood as restrictions. In the following description, the same reference numbers are used for the same or corresponding elements and repetitive description is largely avoided.
A handheld setting tool for driving or setting a nail or bolt into a substrate (e.g. steel or concrete) according to one embodiment comprises a drive or a piston drive, preferably a gas spring drive or an electrodynamic drive, which drives an actuator 11. The driven actuator 11 serves to drive the nail or bolt into the substrate. The handheld setting tool further comprises a decoupling device which at least partly or partially decouples a first movement process of a first moving part or piston 111 in the actuator 11, driven by the drive, from a second movement process of a second moving part or piston 112 in the actuator 11 for driving or setting the nail or bolt. (To aid understanding, the reference numbers refer here only by way of example to features in
The decoupling device may advantageously be designed in such a way that kinetic or translatory energy (caused by the drive) of the first moving part or piston 111 is transferred to the second moving part or piston 112, and kinetic or translatory energy of the second moving part or piston 112 is used to drive the nail or bolt.
The drive (gas spring drive or electrodynamic drive, as explained in detail below) thus serves to drive an actuator 11, in other words a stroke control element, which in this case can be configured as a pneumatic actuator.
The decoupling device here decouples a movement process of the first moving part (e.g. an armature) or the first moving piston 111 effected by the drive (e.g. a translatory movement of the moving part/piston in a cylinder) from a movement process of the second moving part (e.g. a setting element) or the second moving piston 112 (e.g. a setting piston).
Partial decoupling of the movement processes can be achieved, for example, by ensuring that a translatory movement of the first piston does not lead directly or synchronously or simultaneously to a translatory movement of the second piston, and vice versa. In other words, the movement process of the first piston preferably leads to a movement of the second piston only after a certain delay. An (immediate) recoil is therefore not directly transferred to the first piston and thus to the drive.
In an advantageous embodiment, the decoupling device may be formed in such a way that the first moving part or first moving piston 111 is not rigidly connected to the second moving part or second moving piston 112, or there is no direct contact between them. The person skilled in the art will recognise that, in this embodiment, a translatory movement of the first piston does not lead directly or synchronously to a translatory movement of the second piston.
In a further advantageous embodiment, the decoupling device may be formed by having a compressible fluid, e.g. air, between the first moving part or piston 111 and the second moving part or piston 112. Compared to an incompressible fluid, where a translatory movement of the first piston due to the incompressible fluid, e.g. lubricant, would directly or synchronously lead to a translatory movement of the second piston, a compressible fluid can at least partially decouple the movement processes of the first and second pistons. The person skilled in the art understands that, for example, only the attainment of a certain shorter distance between the first and second piston, combined with a compression of the compressible fluid, causes the moment of inertia of the second moving part or piston to be overcome, so that it can be moved for the setting operation.
Advantageously, a stroke length (distance between a first and second dead centre) of the first moving part or piston 111 is independent of a stroke length of the second moving part or piston 112. This allows the nail driving energy (nail setting energy) of the drive to be set independently of a setting stroke of the second moving part or piston 112.
In a further advantageous embodiment, the actuator 11 may further comprise a cylinder, wherein the first piston 111 and the second piston 112 are disposed opposite one another in the cylinder, and wherein at least one piston seal is formed in the cylinder. The piston seals may be one or more piston rings and/or a gas dynamic seal. The gas dynamic seal is preferably of the labyrinth piston seal type (as will be explained further below).
In a further advantageous embodiment, the actuator 11 may further be designed such that a resetting device (e.g. a spiral compression spring) is formed for the second moving part or the second moving piston 112. After driving (setting) the nail or bolt, the second moving part or the second moving piston can thus be returned to an initial position, largely independently of the first moving part or the first moving piston of the actuator 11.
In a further advantageous embodiment, the drive may comprise a further actuator 10. The actuator 10 is, for example, part of a gas spring (as further explained below) and is coupled to the first moving part or piston 111 so that the driven further actuator 10 leads to the first movement process in the actuator 11. In this embodiment, the setting stroke of the second moving part or piston 112 in the actuator 11 is independent of a travel of the further actuator 10, so that the nail driving energy (nail setting energy) can be set independently of the setting stroke with which the nail or bolt is driven.
The handheld setting tool shown in
The pneumatic actuator 10 is movable between a stroke start position range, in which the gas spring is under maximum tension, and a stroke end position range, in which the gas spring is at least partially relaxed. The person skilled in the art will recognise that this driven movement of the pneumatic actuator 10 causes a movement of the moving part or piston 111 in the actuator 11 (first movement process), but this movement is at least partially decoupled from the movement of the second moving part or piston 112 (second movement process).
In other words, the pneumatic actuator 10 (first actuator), together with the working gas reservoir 20, forms a pretensioned gas spring and thus the gas spring drive. To tension the gas spring, the motor 70 is supplied with electricity from the energy store 90 (e.g. a rechargeable battery or fuel cell) via the motor controller 80. The motor 70 drives the reduction gear 60. The reduction gear 60 drives the tensioning device 50. The tensioning device 50 translates the rotational movement of the reduction gear 60 into a translatory movement, acts on the piston rod 01 of the pneumatic actuator 10, and moves its piston in such a way as to convey working gas from the pneumatic actuator 10 into the working gas reservoir 20, i.e. to tension the gas spring. The lock 40 is able to lock the gas spring in the tensioned state. In order to drive the nail or bolt 140, lock 40 is released, for example by means of an electromagnetic actuator 41. The volume that is displaced by the piston of the pneumatic actuator 10 when the gas spring is tensioned is referred to as the stroke volume. Further optional components of a setting tool according to
Reference number 30 represents a valve which is able to connect the working gas reservoir 20 and the pneumatic actuator 10 to one another. It can be positively controlled with a fast electromagnetic actuator 31, e.g. according to DE 10 2009 031 665 A1, plus a spring, to conduct a gas pulse from the working gas reservoir 20 into the actuator 10 and close it again before the driving process is completed, the valve preferably opening automatically when the pressure in the displacement chamber of the actuator 10 exceeds a certain value which is greater than the pressure in the working gas reservoir 20. The person skilled in the art understands that the recoil of the tool can be reduced in this way when driving into solid substrates, and the user can vary the nail driving energy by selecting the valve opening time; however, this is at the expense of the tool's electrical efficiency. The valve 30 can preferably also be formed by the piston of the actuator 10, which then serves as a shut-off element or has such an element, the cylinder of actuator 10 being designed to incorporate a valve seat, sealing being effected with the aid of force from the lock 40, which can, for example, have a spring or be of resilient design in order to generate force (this variant will be explained later with reference to
Reference number 120 represents a thermocouple that can be used to measure the temperature in the working gas reservoir 20. Reference number 100 represents a manometer, in particular an electric or electronic manometer, with which the static pressure in the working gas reservoir 20 can be measured. Reference number 21 represents a second working gas reservoir which is normally subject to overpressure in relation to working gas reservoir 20 and whose static pressure can be measured, for example, by means of a manometer 101. The purpose of working gas reservoir 21 is to compensate for any leakage losses in working gas reservoir 20. This can be achieved via a pressure reducing valve 32. For temperature compensation, the working gas in working gas reservoir 20 can be heated or cooled, for example by a Peltier element 110 (in place of which a heat pump can also be used, for example), which also creates a thermal connection between the working gas in working gas reservoir 20 and the environment with the cooling or heating elements 111 and 112. Reference number 130 further shows a valve via which working gas reservoir 21—the “top-up reservoir”—can be filled with working gas from outside.
In a particularly advantageous embodiment, the piston of actuator 10 with piston rod 01 does not itself act (directly) on the nail or bolt 140 to drive it in. Instead, the actuator 10 acts with its piston rod 01 on a striking mechanism, whereby kinetic energy (including parts mechanically connected thereto) of the actuator 10 can be transferred from the first piston (e.g. piston 111 in
For example, a first piston 111 is driven with the help of actuator 10 (first actuator) via piston rod 01 in a further pneumatic actuator 11 (“striking mechanism”, second actuator), which can be filled with air (ambient pressure), for example. In addition to the first piston 111, the pneumatic actuator 11 has a second piston 112, as shown in
To achieve sealing, the first and second pistons of actuator 11 can be designed in the manner of pistons of labyrinth piston compressors, so that the necessary—temporary—sealing can be effected gas-dynamically.
To drive a nail or bolt 140, by releasing lock 40, the piston rod 01 and thus the piston of actuator 10 as well as the first piston 111 of actuator 11, which is connected to piston rod 01, can be accelerated by the pretensioned gas spring. This increases the pressure between the first and second piston of actuator 11 almost exponentially: momentum and kinetic energy are transferred by the gas buffer formed between the first and second piston of actuator 11 from the directly gas-spring-driven part of the setting tool (piston 101 of actuator 10, piston rod 01, first piston 111 of actuator 11) to the second piston 112 of actuator 11 and consequently also to its piston rod and associated parts (for example the return spring). This requires the moving masses to be expertly matched with one another, taking any reduced masses into account. The nail or bolt 140 is thus ultimately driven via the piston rod of the second piston 112 of actuator 11. If this second piston 112 of actuator 11 is double-acting, i.e. if the side of the cylinder of actuator 11 facing the nail is closed sufficiently tightly, a second fluid or gas cushion for returning the second piston can be built up during a setting operation in the cylinder of actuator 11 on the side of the second piston 112 facing the nail (as shown in
There should be a clearance between the piston rod of the second piston 112 of actuator 11 driving the nail or bolt 140 and the nail 140 itself in order to allow sufficient momentum transfer (preferably at least 50%) from the first to the second piston of actuator 11 before the acceleration and eventual driving of the nail even begin: the driving energy preferably comes mostly from the kinetic energy of the second piston of actuator 11 (including its piston rod etc.).
In order to achieve an actuator 11 of short overall length and/or to necessitate only a small clearance between the piston rod and the nail, the energy transfer from the first to the second piston of actuator 11 should be as abrupt as possible, which can be achieved in at least two practicable ways: (i) Firstly, one or more vent openings may be disposed in the cylinder such that the first piston can start to move and convey gas or air through this (these) opening(s), for example into the tool housing, so that initially the movement of the first piston does not lead to a significant increase in pressure in the space between the first and second pistons. Only when the first piston 111 in the actuator 11 accelerated by the piston drive or its actuator 10 passes over the vent openings are these openings largely closed, as a result of which a much greater, in particular steeper-flanked, pressure increase can occur in the space between the two pistons of the actuator 11 than would be the case in the absence of the vent opening(s). (ii) Secondly, the second piston 112 of actuator 11 can be blocked by means of a mechanism such that it can only start to move after exceeding a certain breakaway force. Such mechanisms can operate in a form-fitting or force-fitting manner and are known, for example, from so-called force limiters and from the breechblocks of guns. Both variants can be combined with one another.
Actuator 11 makes the setting stroke and the travel by which the pre-tensioned gas spring (formed by actuator 10 and working gas reservoir 20) is tensioned largely independent of one another. This makes it easier to provide variable driving energies: it is merely necessary to adjust the travel by which the gas spring is tensioned, and thus the stroke volume, accordingly. This does not change the setting stroke, which is determined by actuator 11.
Further aspects of embodiments relating to design features of components of setting tools according to the invention are explained below.
As explained in detail below, the third piston 10a comprises a plurality of piston rings 15a, wherein cavities 16a are arranged axially, i.e. along the direction of movement of the third piston 10a, between the piston rings 15a, or the piston is configured to have such cavities, the cavities 16a being preferably partially, but not completely, filled with an incompressible fluid.
In
In
The plurality of cavities in the form of a cascade (i.e. cavities one after another so that the effect of each cavity is derived from a preceding cavity and acts on a succeeding cavity), as well as providing reliable lubrication, also allow the pressure being sealed to be evenly distributed among the various seals. The contact pressure per seal can be reduced accordingly, therefore the p*v stress of each individual seal can be lessened accordingly. In the initial stroke position shown in
It is proposed that piston 10a and cylinder 12a be made from a sufficiently tough, hard, particularly wear-resistant and highly polishable steel. Highly suitable materials include steels such as 1.4108, i.e. cold-work steels and in particular pressure-nitrided steels with a very fine martensitic structure, further characterised by the absence of coarse-grained carbides or carbonitrides, where “coarse-grained” is understood to mean a maximum extension in one direction of more than 20 μm and preferably more than 10 μm, including in the case of linearly precipitated carbides.
Preferably, when using steel 1.4108 (material number) for piston 10a and cylinder 12a, a slightly higher Rockwell hardness is set for cylinder 12a than for piston 10a (e.g. 56-58 HRC for the piston, 58-60 HRC for the cylinder or its running surface) by means of an appropriate tempering treatment.
In addition to the cold-work steels mentioned above, newer materials that can be processed to near net shape using additive manufacturing methods (e.g. laser sintering) are also particularly suitable for pistons and/or cylinders. In particular, very hard powder-metallurgical steels of sufficient toughness (e.g. Vibenite 290) and metallic glasses based on elements of the fourth group should be mentioned here.
Piston 10a and the running surface of cylinder 12a can very preferably be coated with hard material layers or tribological layers. CVD-deposited, predominantly tetrahedrally coordinated carbon (ta-C) is particularly suitable for coating cylinder 12a or its running surface. Suitable coatings for the piston 10a are also ta-C, but also a-C/WC, TiN, TiMoN (as solid phase solution or MoN/TiN “superlattice”), TiN—MoS2, as well as the nitrides, carbides and carbonitrides of Cr, Ti, Zr, Hf and also aluminium oxide (and/or aluminium oxynitride) in amorphous form or as nano- or microcrystalline corundum. Particularly suitable materials for the piston rings are expertly selected, in particular temperature-resistant and abrasion-resistant plastics from the group of polyetheretherketones (PEEK) and/or polyimides (PI), and/or ultra-high molecular weight polyethylene (UHMWPE), and/or liquid-crystalline polyethylene terephthalate, preferably filled with solid lubricants such as PTFE and/or graphite and/or hexagonal boron nitride (hBN) and/or MoS2, and if necessary (in particular ceramically) reinforced, in particular with glass fibre, carbon short fibre, pyrogenic silica; further preferably, the piston ring material is also selected to have a low coefficient of sliding friction with the friction partner, i.e. the running surface of cylinder 12a, and preferably not to form any significant adhesion with the latter, and even to have relatively high thermal conductivity and a low coefficient of thermal expansion. Carbon-based materials are particularly suitable for the guide rings, for example antimony-impregnated graphite.
A skilled implementation of an actuator 10 (from
As explained in detail below, the pneumatic actuator 10 comprises, in addition to the third piston 10b, a fourth piston 11b, wherein a reservoir 13b is formed between the third piston 10b and the fourth piston 11b, which reservoir 13b is filled with an incompressible fluid which preferably has the properties indicated below and is adapted to the working gas as explained below.
This embodiment according to
The gear wheels can be rotated by an electric motor with reference number 70 in
The ratchet freewheel comprises driving members 21c, which are rotatably mounted and have a stop or some form of detent, whereby in one direction of rotation of 20c the piston rod 10c is moved with it when driving member 21c and lifting member 11c of the piston rod intermesh. In the opposite direction of rotation of 20c, however, driving member 21c can be moved over the lifting members 11c largely without resistance by moving the driving member about its axis of rotation sufficiently to allow the lifting member to pass. This condition is shown in
The driving members are preferably formed as ratchets of a ratchet freewheel and can be configured to match corresponding lifting members (e.g. “teeth”) on the piston rod, thereby avoiding linear loads between driving and lifting members as far as possible and aiming for surface loads (Stribeck pressure rather than Hertzian stress).
In addition to the driving members and their rotatable mounting with stop/detent device, the freewheel also includes means for returning the driving members from a give-way position (as shown in
By means of actuator 11 (second actuator) from
As explained in detail below, the pneumatic actuator 10 here comprises a cylinder 12f, the cylinder 12f being configured to incorporate a valve seat 13f, the third piston 10f being configured to act as a shut-off element for this valve seat or to incorporate a corresponding shut-off element, so that the third piston 10f and the cylinder 12f together form a valve which can be closed by pressing, by means of sufficient external force, the third piston 10f and thus the shut-off element against the valve seat 13f formed by or attached to the cylinder 12f.
In
Further aspects relating to embodiments of the invention which are particularly helpful in enabling the person skilled in the art to carry out the invention are explained below: For the motor 70, so-called brushless DC motors, preferably those of axial flux type, are particularly suitable. These achieve the highest power densities with high electrical efficiencies, and their polarisation by the permanent magnets causes a sufficient cogging torque—after reduction by gear 60—to hold a tensioning device 50 according to
The working gas reservoir 20 preferably encloses a volume Va, to which the following applies with regard to the maximum stroke volume Vh of actuator 10 in
Nitrogen that is as dry as possible is suitable as working gas (“as dry as possible” is here to be understood as meaning that dew formation can be reliably excluded over the entire operating range). The use of light gases (which de facto means helium, since hydrogen is hardly an option due to its reactivity [flammability, possibly also the danger of hydrogen embrittlement]) instead of nitrogen offers the advantage that, due to their high sonic velocity, the gas dynamics play a subordinate role even at relatively very high piston speeds: With heavy gases and high piston speeds, during a driving process resulting from the piston movement a not insignificant drop in the working gas pressure felt by the piston head (the working piston of actuator 10) initially occurs, followed by a pressure increase (“overshoot”) during the subsequent abrupt deceleration of the piston; this process is associated with irreversibilities, thus reducing efficiency, and also distributes force unfavourably over the travel of the gas spring.
On the other hand, polyatomic gases, and in particular more than diatomic gases such as CF4, offer the advantage of having a lower isentropic exponent, which, given the same initial conditions and the same compression ratio, leads to a lower temperature increase of the working gas during compression (i.e. the tensioning of the gas spring) and thus to lower heat losses—and consequently to lower irreversibilities—than is the case with monatomic gases. Gas mixtures should also be considered. For example, CO2 can be added to nitrogen to increase the isentropic exponent of the gas mixture. The use of CO2 as working gas (working medium) also offers the advantage of being able to store working medium at a very high density in a top-up reservoir (reference number 21 in
The cylinder and working gas reservoir can be understood as a piston drive and suffer from a fundamental problem where setting tools with setting pistons are concerned: the abrupt movement of the piston mass can cause a pronounced muzzle flip of the setting tool during the setting operation, in particular while the nail or bolt is being driven, which can reduce setting quality.
With regard to fastening quality, this problem is also generally known and has previously been addressed, see e.g. WO 2019/121016 A1.
The strong muzzle flip and recoil also place a high physical strain on the operator. The reason for the muzzle flip is, on the one hand, that the extended movement path of the piston's centre of gravity does not usually meet the centre of gravity of the setting tool. On the other hand, holding the setting tool by a handle, which is also next to the movement path of the piston's centre of gravity, gives a pivot point D1 (constraint). A known result is that the setting tool bounces up and back harshly during a setting operation, and also while driving in. The present invention is not immune to this problem.
However, the described problem can at least be largely remedied, as shown below by way of example, such example again being in no way to be understood as restrictive:
The setting piston 610 (e.g. the second moving part or piston 112 (from
The piston drive 600 (e.g. gas spring drive, electrodynamic drive or similar) is thus configured here such that, on the one hand, it has a substantially higher mass than the piston 610 itself, preferably at least four times the mass and particularly preferably more than ten times the mass.
The piston drive 600 (here this may include, for example (see
In contrast to the state of the art, the described method not only improves nail driving quality but also greatly reduces the bio-mechanical stress on the operator, especially with regard to force peaks occurring during the setting operation, which can prevent fatigue and injuries.
Due to the components necessary to realise this method, a setting tool that is damped using the above method is naturally heavier than one that is undamped. However, the additional weight is likely to be in the range of 3 . . . 10% of typical setting tools. Setting tools designed according to the main claim of this application are characterised by a high nail driving energy density and can in any case be more lightly constructed than conventional pneumatic setting tools, for example. The piston drives of combustion-powered and in particular powder-actuated setting tools as well as those based on electrodynamic drives (e.g. Thomson coils) can have very high gravimetric nail driving energy densities and/or very high rates of force increase on the piston, so that the damping method described above also appears particularly useful for such devices to protect operators from fatigue and injury.
The latter may become even more relevant in the future due to stricter occupational health and safety requirements.
Due to friction and, where applicable, the force of, for example, a return spring 660, a certain, slight muzzle flip will still result due to the holding of the handle 630 and the resulting centre of rotation D1 at the joint 670; to reduce this further, the extended path of the centre of gravity S1 of piston 610 cannot be guided exactly through the centre of gravity of piston drive 600, but can rather be shifted slightly towards the centre of rotation D1 in parallel with the direction of movement of the piston.
Other setting tools besides those with a gas spring can also be realised with a decoupling device such as that formed with the help of an actuator 11 from
Against this background, a further embodiment of a hand-held setting tool comprises an electromagnetic drive, preferably with a Thomson coil actuator e.g. according to WO 2018/104406 A1 (see e.g. FIG. 1 of that patent), i.e. an electrodynamic drive with a first excitation coil, a soft magnetic frame, and a squirrel cage rotor and squirrel cage winding movably mounted along an axis, wherein the soft magnetic frame has a saturation flux density of at least 1.0 T and/or an effective specific electrical conductivity of at most 10{circumflex over ( )}6 S/m. In this electromagnetic drive, the frame is designed as a “flux concentrator”, the first excitation coil being directly or indirectly supported on the frame and formed, for example, from fibre-reinforced flat wire. In this embodiment, the handheld setting tool further comprises the decoupling device explained above, wherein the movably mounted squirrel cage rotor or movably mounted squirrel cage winding is formed in a (e.g. slidingly mounted) movable element (piston, armature) which effects the movement process of the first moving part or piston in the actuator (“striking mechanism”). As explained above, the movement process of the first moving part or piston, effected or driven by the moving squirrel cage rotor, is at least partially decoupled from the movement of the second moving part or piston in the actuator for driving the nail or bolt, leading to a reduction of the recoil when driving into solid substrates.
Another alternative embodiment of a hand-held setting tool comprises an electromagnetic drive according to for example WO 2012/079572 A2 or WO 2014/056487 A2 (as further explained below), i.e. an electromagnetic drive comprising at least a first coil and a second coil, wherein the first coil is formed on or in a flux concentrator and the second coil is a moving coil. In this embodiment, the moving coil is formed in or on a moving element (piston, armature) that effects the movement process of the first moving part or piston in the actuator (“striking mechanism”). As explained above, the movement process of the first moving part or piston, effected or driven by the moving coil, is at least partially decoupled from the movement of the second moving part or piston in the actuator for driving the nail or bolt, resulting in a reduction of the recoil.
Via these embodiments, problem (A) is eliminated by the decoupling device.
Problem (B) concerning electrodynamic drives with moving coils can also be solved by the decoupling device, since with an electric drive having a short, limited stroke (compared to the setting stroke), the stranded wires can be much shorter and are accordingly subjected to lower inertial forces during operation; furthermore, the supply of electricity to the moving coil(s) can if necessary be solved by sliding contacts.
Problem (C) can also be solved by the decoupling device, as the deceleration of the armature (“piston”) now takes place in a defined manner: due to the gas cushion formed between the two pistons of actuator 11 during a setting operation, the “armature” or piston of the electric actuator, for example, does not encounter a hard stop.
In further embodiments of electrodynamic drives with moving coils, resetting the drive can be achieved in a simple manner: To drive a nail, the coils are at least temporarily energised in opposite directions (particularly preferably with the aid of capacitor discharge), so that repulsive forces act between the coils. The opposing current flow preferably also leads to a mutual compensation of the resulting electromagnetic far field, so that lower demands are placed on the shielding properties of the setting tool's housing. To reset the drive, on the other hand, the coils can be energised in the same direction so that an attractive (Lorentz) force acts between the coils.
The reference numbers in
To drive a nail or bolt into a substrate with the arrangement schematically illustrated shown in
After reaching the desired charging voltage via C1, the thyristor SCR can be fired to drive a nail. Current now flows via the supply cables 700 into the (flat) coils. Both coils are preferably connected in series in such a way that the current in both coils flows in opposite directions during the setting operation, i.e. they repel one another. Flat copper wire is particularly suitable for the coils in order to achieve the highest possible fill factor with minimal electrical resistance.
The supply cables 700 can be guided directly through piston 720 or its (rear) “guide axis”; very preferably, the supply cables consist of an aluminium alloy or copper, in particular in the form of fine, highly flexible stranded wires, and are strain-relieved outside piston 720, for example with the aid of carbon fibres or carbon fibre fabric: the decisive point is that the strain relief connected mechanically in parallel with the supply cables is made from a material of sufficient tensile strength—i.e. does not break under the given conditions—and has a higher tensile modulus than the electrical supply cables themselves which it is intended to relieve. The strain relief is preferably designed to protect the electrical conductors from a tensile stress (during or as a result of a setting operation) that exceeds their yield point or even their tensile strength. Further preferably, the material of the strain relief should have high specific strength. Carbon fibres and carbon fibre fabrics are able to meet these requirements. The drive piston 720 (first piston) is configured to form an actuator 11 with the setting piston 730 (second piston) and cylinder 780, i.e. a decoupling device as explained above (e.g. according to
The preferably gas-dynamic seal designed in the manner of pistons of labyrinth piston compressors is not shown in
The invention can be practically implemented as follows: The drawing, including the circuit diagram, is converted into a FEM model and the geometry is parameterised, with corresponding (material) properties assigned to the individual components mentioned in the list of references. Real properties are assumed for the electrical components, therefore the circuit diagram is mapped in the model with a corresponding equivalent circuit diagram. For the gas compartments, at least the Van der Waals equation is applied and solved in order to approximate the corresponding gas forces on the surfaces; where appropriate, the gas dynamics can also be taken into account. The first flat coil 711 and the second moving flat coil 721 preferably have the same number of turns, so that they always generate (almost) equal magnetomotive forces as a result of their series connection. Parametric optimisation is then carried out (“parametric sweeps”), taking into account constructive, e.g. production-related requirements such as minimum wall thicknesses, representable (flat) wire thicknesses etc.; otherwise, (all) geometric parameters and the number of windings are varied and a Pareto optimum is sought, also taking into account the prices of parts, components and materials, and approval requirements (EMC, EMCE, etc.). Starting from the optimum arrived at in this way, a mechanical engineering design can then be produced, which will deviate from the initially simple FEM model due to issues of assemblability and production, will be more complex and may include further components that have to be taken into account. A new parametric FEM optimisation is then carried out on the basis of this design. This process, expertly carried out, results in an extraordinarily efficient setting tool after only a small number of iterations. For example, drives with a magnetic circuit having a diameter of only d=60 mm can easily achieve driving energies of over 500 J with efficiencies in the region of 50%. Up to now this energy range has been reserved for combustion-powered setting tools, in particular powder-actuated tools.
Further embodiments are given by:
E1. Handheld setting tool for driving nails or bolts into a substrate, comprising:
E2. Setting tool according to E1, characterised in that the setting tool is dimensioned such that, during a setting operation, the maximum kinetic energy of the moving parts of actuator 10, expressly comprising all parts permanently attached to the piston of actuator 10, reaches at least half of the driving energy ultimately acting on the nail.
E3. Piston for a pneumatic actuator and in particular a gas spring, characterised in that it comprises a plurality of piston rings, and in that axially, i.e. along the direction of movement of the piston, cavities are disposed between the piston rings or the piston is configured to have such cavities, which are preferably partially but not completely filled with a lubricant.
E4. Piston for a pneumatic actuator and in particular a gas spring, characterised in that it comprises a plurality of pistons, for example two pistons, not rigidly connected to one another, between which there is a fluid.
E5. Piston for a pneumatic actuator according to E4, characterised in that the fluid is a liquid lubricant.
E6. Piston for a pneumatic actuator according to claim E5, characterised in that the fluid is a non-Newtonian fluid, in particular a shear-thinning fluid, which preferably also has thixotropic properties.
E7. Piston for a pneumatic actuator according to E6, characterised in that the non-Newtonian and in particular structurally viscous fluid, which is preferably also thixotropic, is produced by dispersing one or more solid lubricants such as, for example, hBN and/or graphite and/or MoS2 and/or dissolving one or more oligomers or polymers in the liquid lubricant.
E8. Pneumatic actuator comprising a cylinder and a piston according to one or more of the pistons described in E3 to E7, characterised in that the cylinder is configured to incorporate a valve seat and that the piston is configured to act as a shut-off element for this valve seat or incorporates a corresponding shut-off element, so that the piston and cylinder together form a valve which can be closed by pressing, by means of sufficient external force, the piston and thus the shut-off element against the valve seat formed by or attached to the cylinder.
E9. Striking mechanism for a setting tool, characterised in that it transmits kinetic energy of a first piston of a piston drive to a moving part, for example a second piston, and the nail or bolt is driven wholly or predominantly by the kinetic energy of the moving part, the first piston and the moving part not being rigidly connected to one another, the first piston and the moving part being decoupled with regard to their stroke lengths.
E10. Striking mechanism for a setting tool, comprising at least a first and a second piston and a cylinder, wherein the pistons are disposed opposite one another, i.e. as in opposed piston engines, in the cylinder, wherein gas-dynamic seals such as, for example, labyrinth seals can preferably be provided as sealing means instead of piston rings, and wherein the first piston is driven to transmit momentum to the second piston via gas located between the pistons, and, for example via a piston rod, the kinetic energy of the second piston can be used to drive in a nail and/or bolt or for percussion drilling.
E11. Striking mechanism according to E10, characterised in that a resetting device is provided for a second piston.
E12. Striking mechanism according to claim E10 or E11, characterised in that the pistons and/or the running surface of the cylinder are hard chrome plated.
E13. Handheld setting tool comprising at least
E14. Handheld setting tool according to E13, characterised in that, in the reference system of the setting tool, the extended paths of the centres of gravity of the piston or pistons are parallel to the extended movement path of a movable piston drive.
E15. Handheld setting tool according to E13 or E14, characterised in that the extended path(s) of the centre(s) of gravity of the piston or pistons pass through the centre of gravity of the piston drive at least during the driving of the nail or bolt, which is to be understood in the present case as meaning that, during the setting operation, the minimum distance of the said extended path(s) from the centre of gravity of the piston drive is always at least five times, but preferably more than ten times, less than the minimum distance of those extended paths from the centre of gravity of the entire setting tool.
E16. Handheld setting tool according to one or more of E13 to E15, characterised in that the setting tool comprises at least one handle, and that this handle is rotatably mounted relative to a part of the setting tool in or on which a piston drive is axially movably disposed, wherein at least one mechanical damper, for example a hydraulic shock absorber or a polymer damper, is provided to dampen a rotational movement between the handle and the part on which the handle is rotatably mounted, wherein a lock can be provided to block such rotational movement while no setting operation is taking place.
E17. Setting tool comprising a striking mechanism according to one or more of E9 to E13, wherein the piston drive is an electrodynamic drive and the mass accelerated by the piston drive is to be understood as a piston or comprises the mass of the first moving part of the striking mechanism according to E9.
E18. Setting tool according to E17, characterised in that the electrodynamic claim comprises at least one excitation coil and at least one moving second coil or a moving squirrel cage winding, which preferably can be disposed on a part made of soft magnetic material movably disposed along an axis of movement, said soft magnetic material preferably having a saturation flux density of at least 1.5 T and further preferably an effective specific electrical conductivity of at most 10{circumflex over ( )}6 S/m.
E19. Handheld setting tool for driving a nail or bolt into a substrate, comprising: a drive 600, preferably a gas spring drive or an electrodynamic drive, driving a setting piston 610 which serves to drive the nail or bolt into the substrate; characterised in that the setting piston 610 has at most a quarter of the mass of the drive 600.
E20. Handheld setting tool according to E19, wherein drive 600 is axially movably disposed in the setting tool, preferably on guide elements 690.
E21. Handheld setting tool according to E20, comprising an openable lock 620 that is configured to fix the piston drive in one or more stroke starting positions; a shock absorber 640, for example a hydraulic shock absorber; a resetting device, for example a return spring that is configured to move the drive relative to the setting tool back from its stroke end position range to a stroke start position, wherein, in the course of a setting operation, the lock 620 opens or can be opened so that the drive 600 can move from a stroke start position A towards the stroke end position range as a result of the recoil experienced by it, wherein this return travel of the drive 600 can be braked by the shock absorber 640, wherein preferably the drive 600 is braked by the shock absorber 640 only after a return travel of a certain return travel distance, and the return travel distance is such that the nail or bolt is predominantly or, preferably, completely driven in before the shock absorber 640 takes effect and brakes the return travel of the drive.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019004422.3 | Jun 2019 | DE | national |
| 102019005599.3 | Aug 2019 | DE | national |
| 102019005792.9 | Aug 2019 | DE | national |
| 102019006714.2 | Sep 2019 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17619714 | Dec 2021 | US |
| Child | 18532095 | US |
