WO2012013225A1 - Gardening shears having a pruner spring and method for producing a pruner spring - Google Patents

Abstract

For gardening shears having a pruner spring for spreading the handle levers, the present invention proposes a design of the spring in which a main spring body comprising a main body that is made of steel and wound helically in the manner of a pruner spring is coated over the entire surface thereof with a first surface coating, which contains a corrosion-reducing material, and with a second coating deposited on the first coating. The second coating can advantageously contain friction-reducing additives and/or colouring additives.

Description

 Pruning shears with a pruning shears and method of producing a pruning shears.

The invention relates to a secateurs with a Rebscherenfeder and a method for producing a Rebscherenfeder.

In secateurs, the hand lever are often urged by a spring in an open position, so that the closed by hand force scissors automatically opens after a cut again. Especially in pruning shears in higher price segments so-called Rebscherenfedern are used as springs. Such Rebscherenfedern are made of a flat, two mutually angled leg having sheet metal blank by spiral winding. The flat sheet metal blank is typically punched out. Typically, after helical winding, the springs are coated with a copper layer and a nickel layer for corrosion protection, but the interposed successive spiral paths do not or only insufficiently face each other at a small pitch, typically less than 0.1 mm, with the copper and nickel layers be coated. This has the consequence that rusting through between the spiral passages moisture of the spring steel there, which on the one hand reduces the life of the springs and on the other can lead to complaints by escaping rust. Hot-dip galvanizing is not possible because it affects the spring elasticity of the spring steel. With a galvanic coating there is the danger of hydrogen embrittlement of the spring steel. The flat sheet metal blanks show, especially in the cost-preferred production by punching punching burrs or sharp edges, which can scratch the adjacent spiral winding, resulting on the one hand to a user unpleasant running behavior and the other by Injury of the protective layers in turn can cause corrosion of the spring steel.

The invention has for its object to provide a pruning shears with an improved Rebscherenfeder and a method for producing such a Rebscherenfeder.

The invention is described in the independent claim. The dependent claims contain advantageous embodiments and further developments of the invention.

It turns out, surprisingly, that despite the narrow gaps between adjacent spiral courses of the wound spring, a coating with particles of corrosion-protecting material is possible and leads to a corrosion protection layer which is better in the gaps. The particles preferably contain zinc which, in the presence of moisture due to its non-steel electrochemical potential, provides long-lasting rust protection even though the coating does not form a perfectly closed surface over the steel surface of the main body of the spring. The particles are preferably platelet-shaped and lie with their plate surfaces approximately parallel to the surface of the main body of the spring and cover it largely.

Suitable materials for producing such corrosion-protective surface coatings, in particular also with platelet-shaped, zinc-containing particles, are known per se and commercially available, for example, under the trade name Delta Tone.

The deposition of the first layer on the steel surface of the main body of the spirally wound spring is preferably carried out by applying a Nes flowable material mixture, which contains at least one flowable carrier material and in this suspended the anti-corrosive particles, on the surface of the main body of the spring, for which the spring is introduced in particular in a dip bath with such a material mixture. The spring removed from the immersion bath with the material mixture adhering to the surface of the base body is exposed to a process step at elevated temperature at which the coating solidifies, in which case a substantial reduction of the volume fraction of the support material of the material mixture and concomitantly a reduction of the layer thickness and an exposure or widening of gaps occurs between adjacent spiral turns of the spring.

Depending on the areal coverage and layer thickness of the first layer which can be achieved in a coating process, this can also be applied by a plurality of coating operations in the form of several successive partial layers.

The second layer applied to the first layer consists of a second material, which is at least partially different from the first material of the first layer, wherein the term material also includes material mixtures such as suspensions and emulsions.

In preferred embodiments, the second layer can contain materials with friction-reducing properties and / or coloring materials. In particular, such materials may, in turn, be part of a material mixture which is preferably applied in a flowable form to the previously produced first layer and preferably solidified in a further process step at elevated temperature. As a friction-reducing material, for example, PTFE particles may be suspended in a flowable carrier material.

For coloring the second layer, pigment particles may advantageously be added to a flowable carrier material for the second layer.

Advantageously, the coating with layers, which are produced from a flowable material by baking a layer applied at higher temperature, has the additional advantageous effect that sharp edges and in particular fine burrs of the steel main body of the spring on the surface of the second layer are rounded and scratching edges on the surface of the radially adjacent spring coil leading to rough running and / or damage to the coating surface is eliminated or greatly reduced, which in turn is beneficial to the life of the spring.

The invention is illustrated below with reference to preferred embodiments with reference to the figures still in detail. Showing:

1 is a flat sheet metal blank for a Rebscherenfeder,

Fig. 2 a wound Rebscherenfeder, Fig. 3 a secateurs with a Rebscherenfeder, an enlarged section with a view in the direction of

Winding axis of the spring, Fig. 5 shows an enlarged section with a view perpendicular to

 Winding axle of the spring.

Fig. 1 shows a planar section FZ of a sheet steel surface, which consists of two obliquely converging legs S1 and S2, which widen slightly in the course of their connection point. Such sheet metal cutouts are typically produced by punching out of a sheet metal surface, wherein sharp edges SK and along these edges sometimes also punching burrs arise. A rebate spring FW of the type shown in FIG. 2 is wound from the flat sheet metal section FZ shown in FIG. 1, wherein the winding axis runs perpendicular to a center plane of the planar blank FZ according to FIG. 1 lying between the two legs S1, S2 and the winding is started from the free ends of the two legs S1, S2, so that these leg ends SE in the wound spring FW according to FIG. 2 are radially inward and axially outward with respect to the winding axis WA.

In the relaxed state of the wound spring FW of FIG. 2, the superimposed and overlapping turns of the helical spring coil are radially spaced from each other by a small amount.

When using a Rebscherenfeder RS as a spring coil FW of the type shown in Fig. 2 in a pruning shears of Fig. 3, the spring between two hand levers H1, H2 of the secateurs is arranged. In Fig. 3, the secateurs is shown in their under the action of Rebscherenfeder RS occupied open Neten state in which the spring RS is already biased in its axial direction. When closing the scissors by moving the two hand lever H1, H2 towards each other, with the scissors mouth between blade SS and counter blade SB closes, the spring RS is further compressed axially and thereby elastically deformed against a restoring force. When the manual force H1, H2 falls or disappears, they are again forced apart under the action of the spring RS into the open position of the scissors shown in FIG. The spring RS typically assumes a slightly curved shape when installed, with individual successive windings being able to abut one another in their overlapping area.

According to the present invention, a steel main body of the spring RS is coated with a first, anticorrosive layer and a second layer above it, wherein the second layer may preferably contain friction-reducing additives and / or coloring additives.

Fig. 4 shows a section of a sectional view through the wound spring with two windings W _n and W _{n +} i of the spiral winding of the main body GK of the spring shown. The main body GK is advantageously made of spring steel. The illustrations are not to be considered as true to scale.

On both opposite sides of the main body GK, a first layer S1 is deposited in each case, which in a preferred embodiment contains particles, in particular platelet-shaped particles of a corrosion-protecting material, preferably zinc. The deposition of the first layer S1 on the steel surface of the body GK is preferably carried out in such a way that the corrosion-protective material is applied as a suspension in a flowable carrier material over the entire surface of the steel surface of the body GK, for which the uncoated wound spring FW advantageously in an immersion bath is introduced, in particular as bulk material of a larger number of springs. After removal from the dipping bath, the steel surfaces of the base body are coated with the suspension adhering thereto. tet. The springs can be subjected to vibration in the dipping bath or afterwards in order to promote the penetration of the suspension into narrow gaps. The removed from the dipping bath, coated with suspension springs can, for. B. in a centrifuge, are freed of excess suspension. The suspension-coated springs are subjected to a process step at elevated temperature, with solidification of the coating with typically simultaneous reduction of the layer thickness. A second layer S2 is deposited on the finished first layer, it being possible for the method steps to be similar to those in the deposition of the first layer, but the material composition of the second layer deviates from that of the first layer. In particular, the second layer may contain additives which reduce friction, such as, for example, PTFE particles and / or coloring additives, such as, for example, pigment articles, which have sufficient temperature stability for a subsequent process step at elevated temperature.

Since, in the relaxed state of the main body of the spring, the overlapping turn sections of successive turns are radially spaced from each other by gaps, the coated spring also shows gap SP between radially successive turns W _n , W _{n +} i in the relaxed state, as in FIG. 4 shown. The mutually assigning surfaces of the second layers S2 cause, even when abutting the spring used in the scissors, in particular with the addition of friction-reducing material, a low mutual friction, so that during operation of the scissors on the one hand a smooth running is guaranteed and on the other a mutual Damage to the coating remains low.

Fig. 5 shows two partially overlapping, successive turns W _n , W _{n +} i of the spiral winding of the spring as a section of a section in a Winding axis WA of the relaxed spring-containing cutting plane. In Fig. 5 is particularly shown that the steel base body GK of the spring by manufacture during punching small, sharp burrs GR may have. These are covered by the materials applied in the flowable state for the layers S1 and S2 and thereby rounded off, so that even when successive turns of the coated spring lie against one another, the ridges GR no longer damage the respectively opposite surface. The sheet thickness of the body GK is typically about 0.15-0.4 mm, the initial radial width of the column of uncoated spring at about 0.1 - 0.3 mm. The layer thicknesses of the first and the second layer are, for example, about 0.004 mm in each case on the finished coated spring. The features indicated above and in the claims, as well as the features which can be seen in the figures, can be implemented advantageously both individually and in various combinations. The invention is not limited to the exemplary embodiments described, but can be modified in many ways within the scope of expert knowledge.

Claims

claims: 1 . Pruning shears with a Rebscherenfeder, the Rebscherenfeder has a spiral-wound from a flat blank metallic base body (GK) made of spring steel, on which on both opposite surfaces, a first layer (S1) with anti-corrosive particles and on this in each case a second layer (S2) is deposited from a different material from the first layer. 2. secateurs according to claim 1, characterized in that the second layer is designed to reduce friction. 3. secateurs according to claim 2, characterized in that the second layer contains embedded in a base material particles of friction-reducing material. 4. Secateurs according to one of claims 1 to 3, characterized in that the second layer is colored. 5. Secateurs according to claim 4, characterized in that the corrosion-protecting particles of the first layer are at least predominantly platelet chenförmig flat. 6. Secateurs according to one of claims 1 to 5, characterized in that the corrosion-protective particles contain zinc. 7. A method for producing a pruning shears for pruning shears according to claim 1, characterized in that after spirally winding a steel base body on its surface successively a corro- sion-protecting first layer and on this one from a different layer from the first layer second layer are generated, wherein after completion of the second layer whose radially facing surfaces are spaced from each other by radial gaps.