EP4108852A1 - Long-life trowel - Google Patents

Abstract

The present invention relates to a tool that can be used for spreading and smoothing building materials, especially plaster and mortar. In particular, it is about a smoothing trowel (10), which comprises a smoothing blade (20) and a handle (30) and in which a handle holder (40) connects the handle (30) to the smoothing blade (20), the handle holder (40) connected to the smoothing blade (20) by a large number of bolts (50), characterized in that recesses (60) are provided in the smoothing blade (20) and the bolts (50) are guided into these recesses (60).

Description

field of invention

The present invention relates to a tool that can be used for spreading and smoothing building materials, especially plaster and mortar. It is typically used for plastering. The tool is generally referred to herein as a smoothing trowel. However, the invention relates equally to spatulas, in particular surface spatulas, painters' spatulas and plaster spatulas, as well as squeegees in individual cases. The invention also relates to corner trowels, inside corner trowels such as outside corner trowels, mortar trowels and pointed trowels, each in toothed and non-toothed versions.

Background of the Invention

The utility model DE 1 754 183 discloses a finishing trowel, the main elements of which are the trowel blade, a handle support and the handle. The grip support attaches to a bar that stabilizes the trowel blade. As the utility model discloses, it can be advantageous to manufacture all three parts in one piece from plastic. This also obviates the difficulty of a reliable connection, as the mechanical stress of the trowels and contact with grout can weaken connections over time.

The disclosure document 1 684 410 discloses a mason's trowel with a soldered connection between the trowel blade and the handle support. The soldered connection is said to lead to improved strength in the connection between the handle and the trowel blade. For this purpose, the solder is introduced into holes in the sole plate of the handle, which are additionally provided with extensions at the end facing the trowel blade. The solution may have proven itself for different blades. But it seems desirable, at least to to have more freedom in the design and choice of material for the handle support and trowel blade, to also be able to offer alternatives to the solder connection.

The disclosure document 25 40 885 discloses a smoothing trowel or "smoothing chip" for plastering with a slidable and replaceable handle. For this purpose, a guide rail is provided on the smoothing blade, to which the handle is attached. The guide rail is attached to the steel finishing blade by welding.

The patent UK 3639978 discloses a mason's trowel in which the handle is arranged behind the trowel blade and is connected to the trowel blade with a curved piece of pipe, the so-called tang. The fastening between tang and trowel blade should be done by welding. This construction may produce a very strong joint, but is poorly suited to other trowel shapes, such as those where the handle is over the center of the blade.

That U.S. Patent 9,784,000 discloses that bolts can be welded onto the top of the trowel blade and a handle can be attached over these bolts.

The invention seeks to circumvent the disadvantages of the prior art. A long-lasting and robust smoothing trowel is to be made available. This should also be able to be produced efficiently.

This object is achieved by a smoothing trowel according to claim 1. Advantageous developments are specified in the dependent claims. Incidentally, these and other advantages can be achieved with a method according to claims 8 to 14 .

In the context of this invention, "smoothing trowel" is also to be understood as a term for designating related tools that are used for distributing building material, in particular those that are named as examples with typical designations at the beginning. A smoothing trowel comprises at least one smoothing blade and a handle. The smoothing blade is usually a completely or mostly flat surface, so that it can be used over the entire surface for smoothing on one level. Exceptions are corner trowels for inner or outer corners/edges, where the smoothing blade is curved so that the two main work surfaces are at a 90° angle to each other.

A handle holder is intended to connect the handle to the trowel blade. The handle holder can be a separate component, alternatively it could be made in one piece with the handle or with the smoothing blade. The handle holder can conveniently be made of a metal, for example steel, stainless steel or aluminium. It is particularly useful here to manufacture the handle holder as a cast component, preferably as an aluminum die-cast component. The handle holder could also be made of plastic, certainly also in the injection molding process.

The handle holder is said to be connected to the trowel blade with a plurality of bolts. A large number is to be understood here as at least one bolt, as a rule at least two bolts, frequently between 4 and 10 bolts, are used. The bolts are advantageously made of metal, for example steel, stainless steel or aluminum. A good weldable metal is an advantage. It is also possible to weld the bolts to the handle holder. It can also be advantageous for the bolts to be screwed. It can be useful to select the bolt material in such a way that a press connection can be achieved.

It is advantageous if the majority of the bolts or all bolts have the same diameter. This makes for an appealing appearance of the trowel and simplifies manufacture. Trowels are available where the first and last bolts of a connecting row of bolts are thicker than the remaining bolts. Since the first and last bolts are more heavily loaded than the other bolts, this can offer advantages. However, the present invention allows a secure and permanent connection without having to choose a thicker first and last bolt.

According to the invention, recesses should be provided in the smoothing blade. These recesses can be round holes, for example. The bolts are inserted into these recesses. Thus, the bolts should not sit on the smoothing blade, but they are at least partially passed through the smoothing blade. This type of connection geometry results in a stronger and more permanent connection than the usual connections with bolts. A smoothing trowel is often used for several years, sometimes for more than a decade. It is exposed to high mechanical stresses, in particular because at least the smoothing blade typically has a certain elasticity. It is also exposed to chemical stresses, especially when in contact with alkaline mortar or plaster.

It is advantageous if the bolts are welded to the trowel. This should be at least some of the large number of bolts used, preferably all of them. It has proven to be particularly advantageous to provide these welded connections on the working side of the trowel and/or in the area of the recesses (ie between the working side and the opposite upper side of the trowel). It may be correct to provide welds on the working side of the screed blade or to provide welds in the area of the recesses or to provide welds on the working side of the screed blade and in the area of the recesses. Individual or all welded joints can be positioned in this way.

There are certain challenges with this approach as it is only then that the smoothness of the sheet has to be restored. At the same time, however, it has been shown that such a connection is particularly strong and durable, as well as favorable in terms of the manufacturing process.

Laser welding, also referred to as laser beam welding, is particularly suitable for connecting the bolts to the smoothing plate. It can be used as heat conduction welding or deep penetration welding. In individual cases, it can be combined with other welding, joining or connection techniques. The connection is preferably made solely by laser welding. Preferably no filler metal is used.

It has proven to be expedient to produce the smoothing plate from chrome-molybdenum steel. In general, it is advantageous to produce the smoothing blade from steel. Particularly torsion-resistant steels come into consideration here. However, these steels also mean that high forces act on the handle and thus the handle holder. It should also be remembered that chrome-molybdenum steel in particular is brittle. A high thermal or mechanical load when connecting the smoothing blade and handle holder should therefore be avoided. This is exactly what is achieved with the present invention. Chrome-molybdenum steel is also used here as a generic term for alloys that contain other (smaller) parts. It is particularly advantageous if nickel is contained in the alloy.

It is expedient if the grip holder has a grip shoe, a grip shaft and a grip core. These can each be designed as separate components or the handle holder can be in one piece. The connection to the smoothing blade is made via the grip shoe. For this purpose, the grip shoe can be cuboid, for example, and on its grip shaft Facing away from the underside have a flat surface for contact and connection with the screed.

The grip shaft serves as a connection between the grip shoe and the grip core. It runs essentially perpendicularly to the contact surface of the grip shoe, ie in the mounted state essentially perpendicularly to the smoothing blade.

The grip core typically runs substantially parallel to the screed blade. Typically, the handle core is surrounded by a handle. The handle can be ergonomically designed. It is often made of plastic, but can also be made of cork, for example. The handle can be made in one piece with the handle core, but it is advantageous if the handle is removable and possibly also replaceable. The handle can then be attached to the handle core and connected to it, for example, wedged or glued or screwed.

It is advantageous if the bolts are connected to the handle holder by pressing. For this purpose, the bolts, if the handle holder has a grip shoe, are inserted into recesses in the grip shoe. The bolts are then compressed under high pressure so that they completely fill the recesses, usually round holes, in the grip shoe. During the pressing process, a bolt cap can also be created, which protrudes beyond the holes in the grip shoe and has a thickening at the top, whereby an additional (positive) connection with the grip shoe is achieved.

1. a. Zurverfügungstellen eines Glättblatts mit einer Oberseite und eine Arbeitsseite
2. b. Zurverfügungstellen eines Griffhalters
3. c. Zurverfügungstellen von Bolzen
4. d. Erzeugen von mindestens einem Loch im Glättblatt
5. e. Einführen des Bolzens in das Loch
6. f. Verschweißen des Bolzens von der Arbeitsseite

The invention also relates to a method for producing a smoothing trowel, which comprises the following steps:

1. a. Providing a smoothing sheet with a top and a working side
2. b. providing a handle holder
3. c. providing bolts
4. i.e. Creating at least one hole in the glazing sheet
5. e. Inserting the bolt into the hole
6. f. Welding the stud from the working side

The steps are performed in the order in which they are listed for convenience. A hole can be produced in the smoothing blade by a machining process, in particular by drilling. The hole can also be created by punching. An equal plurality of holes (or general recesses) is to be provided for the plurality of bolts. It is advantageous if these are generated in a single work step.

It is usually very helpful to equip the handle holder with at least one stud before welding, usually best with all studs to be welded. After inserting the bolts into the respective holes, it can be useful to provide them with a holder there. The bracket can stabilize the stud in the proper position for welding. After welding, the bracket can be removed. There are a variety of tools that can be used to hold it. A mechanical holder can also be provided as a support, which temporarily supports the bolts in an appropriate manner, for example by supporting them from the top of the screed blade. (The top is the opposite side from the work side.) The handle holder itself can serve as a support in this step of the process.

It may generally be convenient to weld the studs from any direction. However, it is particularly advantageous to weld the bolts from the direction of the working side of the trowel. It is fundamentally advantageous for processes for the production of smoothing trowels if the feeding direction of the studs and the direction from which welding is carried out are opposite to each other. For example, the first direction (feed direction) may be in a first hemisphere and the second direction (welder approach direction) may be in a second hemisphere, and both hemispheres are opposed to each other about a central axis. For example, the first direction (direction of feed) can lie in a first right circular cone and the second direction (direction of approach of the welding machine) can lie in a second right circular cone and both circular cones are arranged opposite one another around a central axis, so that they form a double cone form. Both circular cones can have a central angle of 90° or less.

It is quite possible that the bolts protrude a certain distance beyond the trowel. However, this distance is usually much less than the bolt length. Therefore, when a plurality of studs are used, particularly more than four studs, and the studs are spaced closer than 5 cm apart, particularly closer than 3 cm or 2 cm, welding studs from the working side is easier. On the top of the trowel, the protruding studs would interfere with the free approach and movement of a welder or torch.

It can be particularly expedient if, in the process, the handle holder is first fitted with bolts and the bolts are then made available together with the handle holder. In a subsequent process step, the handle holder would then have to be taken to the welding site together with the bolts. However, the welding process itself can be carried out more quickly by preparing the handle holder accordingly. This is particularly advantageous when the welding devices used are expensive and insofar as a high throughput at the welding station is advantageous.

In particular, it is expedient if the bolts are welded by laser welding.

It is advantageous if the bolts used protrude beyond the working side of the trowel and bolt material is removed there during the welding process. It is particularly advantageous if the bolt material is placed in the gap between the bolt and the hole. Material can be melted for this purpose. All or part of the material protruding from the work side can be offset. In this way, the hole, which must be at least minimally larger than the bolt circumference, is completely or partially closed. The movement of material can be facilitated by the action of gravity if the bolts are oriented appropriately. It is therefore useful if the bolt ends point upwards.

The closure could be effected by a welding filler, for example a welding wire, but within the scope of the present invention welding without welding filler is preferred. The welding process without welding filler is even more economical and faster to carry out.

A bolt protrusion is not advantageous per se and in this respect this process concept is not intuitive. Nevertheless, within the scope of the present invention, it has proven to be advantageous to accept the occurrence of a bolt protrusion in the corresponding method step.

A method is also advantageous in which at least two or all of the holes to be provided in the smoothing blade are produced in one work step.

The method is to be understood in relation to the smoothing trowel according to the invention. That is, features of the design of the product are analogous be transferred to the process, and features of the process are to be transferred analogously to features of the product

Fig. 1

zeigt in perspektivischer Ansicht eine einsatzbereite erfindungsgemäße Glättkelle.

Fig. 2

zeigt in gleicher perspektivischer Ansicht eine erfindungsgemäße Glättkelle mit abgenommenem Handgriff.

Fig. 3

zeigt in einer Querschnittsansicht die Aufnahme eines Bolzens durch das Glättblatt.

Fig. 4

zeigt in einer vergrößerten perspektivischen Ansicht einen Abschnitt der erfindungsgemäßen Glättkelle.

Further features, but also advantages of the invention, result from the drawings listed below and the associated description. In the figures and in the associated descriptions, features of the invention are described in combination. However, these features can also be included in other combinations by an object according to the invention. Each disclosed feature is therefore also to be regarded as being disclosed in technically meaningful combinations with other features. Some of the illustrations are slightly simplified and schematic.

1

shows a perspective view of a ready-to-use smoothing trowel according to the invention.

2

shows a smoothing trowel according to the invention with the handle removed in the same perspective view.

3

shows a cross-sectional view of a bolt being received by the finishing blade.

4

shows a portion of the finishing trowel according to the invention in an enlarged perspective view.

figure 1 shows a smoothing trowel according to the invention in a perspective view. The smoothing trowel 10 has a smoothing blade 20 which is guided with the handle 30 . The handle holder 40 is used to connect the handle 30 and the smoothing blade 20 . The handle holder 40 is connected to the smoothing blade 20 by a large number of bolts 50 .

figure 2 shows a smoothing trowel 10 according to the invention in the same perspective view, but in which the handle 30 has been removed. As a result, the design of the handle holder 40 can be seen more clearly. The grip holder 40 includes the grip shoe 42. The grip shoe lies directly on top of the smoothing blade 20. (An indirect bearing over an intermediate layer is also conceivable.) It extends over a substantial part of the length of the smoothing blade, expediently generally over more than 50% of the length, typically between 50 and 80% of the length of the smoothing blade. The grip shoe 42 is connected to a grip shaft 44 that projects from the grip shoe 42 . The handle shaft 44 connects to the handle core 46 . The handle core 46 is suitably a rod or tube section. It has substantially the length of the handle 30. The handle core 46 can have a profile, for example a square or rectangular profile, which prevents twisting of the handle about the longitudinal axis of the handle core 46. A square profile is shown here. A thread can also be provided at the end of the handle core, for example, via which the handle 30 can be secured with a nut in order to prevent it from slipping off the handle core 46 .

figure 3 shows a schematic representation of the connection of a bolt 50 to the smoothing blade 20. The bolt has a lower end 52, a bolt shank 54 and the bolt head 56. In the smoothing blade 20, the recess 60 is provided for the bolt. In the case of a round bolt, this recess is expediently provided as a round hole. The recess can be produced by drilling or punching.

The lower pin end 52 is pushed all the way through the recess 60 from the top of the screed blade 20 . Therefore, the lower pin end 52 of the pin 50 then protrudes and protrudes beyond the working surface 70 of the finishing blade 20.

This positioning of the bolt differs greatly from known connection types. It is typical for the welding that the bolt is placed on top of the smoothing blade 20 . In this variant, therefore, no recess is to be provided at all. In principle, a form-fitting connection would also be conceivable. For this purpose, the lower bolt end 52 could have a thickening and a region of the recess could have a corresponding widening. However, this approach has been studied in more detail and has proven to be disadvantageous, especially in terms of its longevity. In particular, when a trowel of small thickness is used, although a stable connection can be established initially, this connection does not remain stable over the period of use. Since the smoothing blade is exposed to pressure during use and regularly bends in the process, such a mechanical connection is heavily stressed. It can happen that the connection then loosens quickly. Incidentally, it usually happens that the connection is no longer completely flat. The end of the bolt then protrudes beyond the working side 70 of the smoothing blade 20 in individual cases, or it retreats behind it. In one case there is a supernatant, in the other case a hollow is formed. Both affect the smoothing result so negatively that the smoothing trowel usually has to be taken out of service.

However, within the scope of the present invention, the bolt 50 is passed through the recess 60 in the finishing blade to provide a welded joint. Such a weld connection can be provided in the first weld region 62 . This welding area lies in the gap between the walls of the recess 60 and the outer circumference of the bolt 50, completely or essentially between the upper side and the working side of the smoothing blade 20. Welding can also be carried out there with a welding additive if necessary. Alternatively or additionally, welding can take place in the second welding area 64 . This welding area is in the exit area of the stud. Welding is therefore carried out directly on the working side 70 of the smoothing trowel 20. A weld seam typically runs along a ring the edge of the recess and thus at the same time ring-shaped around the bolt. A round hole results in a round ring. Can be welded with the help of a welding filler. Alternatively, welding can also be carried out without welding filler. It can be expedient to melt off part of the bolt material, in particular parts of the protruding bolt material, and use it to form a weld seam.

In this way, a very strong and permanent connection of the bolt 50 to the smoothing trowel 20 can be connected.

A connection to the handle holder 40 is established with the area of the bolt protruding on the upper side of the smoothing trowel 20 , essentially with the bolt shank 54 . For this purpose, the bolt shank 54 is guided into corresponding holes or recesses in the grip holder, typically the grip shoe 42 . The connection can be made by screwing. A thread would then have to be provided on the bolt shank 54 . The connection can also be made by pressing. In the process, so much pressure is exerted on the bolt from the direction of the bolt head 56 that it fills a correspondingly dimensioned recess in the handle holder. A softer bolt material, for example aluminium, should be used for the purpose of pressing.

figure 4 shows with an enlarged section how the connection between the smoothing blade 20 and the handle holder 40 can be established. A plurality of bolts 60 are connected to the screed blade 20 as shown. A number of two to twelve bolts is generally expedient within the scope of the present invention. The bolts are connected to the screed blade 20 at regular or variable intervals. The bolts are then inserted into appropriate recesses in the handle bracket 40, preferably in the handle shoe 42. Shown are bolts which were pressed. Accordingly, it is not necessary to bolt 60 on top to provide nuts. It is expedient if the upper side 48 of the grip shoe 42 is ground down after pressing. Then, as shown, the bolts 60 end flush with the upper side 48 of the grip shoe 42.

Overall, it can be seen how an expedient device that is suitable for mass production and can be used universally can be produced in a cost-effective manner.

Reference List

10

smoothing trowel

20

flat sheet

30

handle

40

handle holder

42

grip shoe

44

grip shaft

46

grip core

48

Top grip shoe

50

bolt

52

lower bolt end

54

bolt shank

56

bolt head

60

recess

62

first welding area

64

second welding area

70

work surface

Claims (14)

A finishing trowel (10) comprising a trowel (20) and a handle (30) and wherein a handle bracket (40) connects the handle (30) to the trowel blade (20), the handle bracket (40) having a plurality of bolts (50) is connected to the smoothing blade (20) by welded joints, characterized in that recesses (60) are provided in the smoothing blade (20) and the bolts (50) are guided into these recesses (60). A finishing trowel (10) according to the preceding claim, wherein welds are provided on the working side of the finishing blade. Smoothing trowel (10) according to one of the preceding claims, in which welded connections are provided in the region of the recesses. A smoothing trowel (10) according to any one of the preceding claims, wherein the welds are made by laser welding. Smoothing trowel (10) according to one of the preceding claims, in which the smoothing blade (20) is made of chrome-molybdenum steel. Smoothing trowel (10) according to one of the preceding claims, in which the bolts (50) are guided in passages in the handle holder (40) and pressed there. A finishing trowel (10) according to any one of the preceding claims, wherein all of the bolts (50) are of the same diameter. Method for producing a smoothing trowel (10), which comprises the following steps: a. Providing a smoothing sheet with a top and a working side b. providing a handle holder c. providing bolts i.e. Creating at least one hole in the glazing sheet e. Inserting the bolt into the hole f. Welding the stud from the working side A method of manufacturing a finishing trowel (10) according to the preceding claim, wherein at least one bolt is provided with the handle holder. Method of manufacturing a finishing trowel (10) according to Claim 6 or 7, in which the welding of the bolt is carried out by laser welding. A method of manufacturing a finishing trowel (10) according to any one of claims 8 to 10, wherein the pin projects beyond the working side of the finishing blade and pin material is placed in a gap between the pin and the hole in the welding process. Method of manufacturing a finishing trowel (10) according to the preceding claim, in which a pin overhang above the working side of the finishing blade is removed. Method for producing a smoothing trowel (10) according to one of Claims 8 to 12, in which at least two holes are produced. A method of manufacturing a finishing trowel (10) according to any one of claims 8 to 13, wherein the direction from which welding is performed is opposite to the direction from which bolts are fed.

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