EP2882910A1

EP2882910A1 - Improved floor stripping device

Info

Publication number: EP2882910A1
Application number: EP13774821.6A
Authority: EP
Inventors: Luc CLAES; Jozef HEIJMANS; Guy MIVIS
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-08-08
Filing date: 2013-08-08
Publication date: 2015-06-17
Also published as: WO2014024160A1; BE1020587A5

Abstract

Disclosed is a coupling piece which is suitable for the transmission of thrust forces between the coupled elements, which is provided with a means by which the coupling piece may be attached in a removable manner to a movable part of a bulldozer suitable for work indoors, and which coupling piece is also provided with a means suitable for being able to receive in a removable and rotatable manner the round stem of a holder for a stabbing knife. Furthermore, an assembly is described of a bulldozer suitable for work indoors with the coupling piece, optionally by means of an accessory piece, preferably also with the holder for the stabbing knife and the stabbing knife itself, as well as a method for the removal of the covering of a surface, preferably an approximately horizontally level plane such as a floor or a roof, which makes use of the coupling piece or the assembly.

Description

Improved floor stripping device

FIELD OF THE INVENTION

The present invention relates to the removal of old and/or worn-out floor or roof coverings from their substrate. More particularly, the invention relates to a device which is suitable for removing floor or roof coverings in existing buildings so that a new covering may be applied on the bare substrate.

BACKGROUND OF THE INVENTION

Buildings are usually solidly built, to persist for long periods. The function assigned to a building or spaces therein may quite rapidly change from that for which the building or space was originally intended and designed.

In order to appropriately arrange the building or a given space for a new function, usually all the elements, which do not contribute or are required for the structural strength of the building, are removed from the building or the space. The designer thus enjoys the greatest possible freedom in rearranging and redecorating the building or space. Non-load-bearing interior walls are thereby removed, with structural steelwork even the outer walls may be removed, and floor coverings are broken out.

An important industry has therefore emerged, which is concerned with the stripping of buildings. However, the stripping of an existing building is not a part of the structural activities of the renovation of a building. It is considered to require little craftsmanship, with the result that the commercial value of this part of the renovation of a building is not highly appreciated. The stripping should therefore be conducted swiftly in order to limit the labour costs.

This stripping should however be carried out with due care, for example without disturbing the structural elements of the building in order not to compromise the robustness of the building. Errors and mistakes in this activity may indeed lead to potentially harmful effects later in the renovation project. In order to keep any dumping costs as low as possible or to exploit the possibilities of recycling as much as possible, it is also important to obtain a good separation of the different removed materials.

Spaces with an economic function change even more frequently as compared to other spaces, of function or decoration. It is thereby important that the space may take on its new economic function as soon as possible. The stripping of the coverings in such areas should therefore be carried out as quickly as possible.

The stripping of buildings is therefore subject to rather stringent requirements of care, coupled with a strict control of the amount of effort required, as well as of the amount of time required for the stripping work.

The removal of old and/or worn floor coverings or roofing represents a costly part of many renovation projects. It is still often carried out manually, which is very time consuming, and physically very demanding for the people performing the work. The requirements for precision are thereby usually even higher, because the substrate is expected to be ready with as little as possible after-treatment, such as an additional equalization, in order to be able to receive the new covering as quickly as possible.

Also floor coverings which are intensely used, such as in sports halls, industrial spaces and hospitals, may rather early be in need of being replaced, even if no new function is assigned to the space.

Coverings such as PVC, linoleum, carpet, rubber coating, vinyl, parquet and planking, roofing, linoleum, ceramic tiles, laminate, are usually glued to the surface. The manual removal of such floor coverings is a time consuming activity, especially when strong glues were used, and in particular with coverings which are rather brittle and readily break apart into smaller pieces, such as for instance linoleum. In order to be able to do this much more quickly mechanically, a seating-on-stripper or Ride-On Mobil ("Fussbodenablosemaschine") has been developed, such as described in WO 201 1/094719 A1. This machine is electrically driven and is extremely agile. It is provided with a stabbing knife which is pushed down below the floor covering to be removed, and is then pushed ahead in front of the machine. The blade of the knife is held horizontally in contact with the floor with some pressure and during the forward pushing breaks the glue layer holding the carpet in place. The device proposed in WO 2011/094719 A1 is however especially designed for stripping floor coverings and cannot be used for other activities required in the renovation of buildings. The proposed device is rather complex, with a combination of an electrical and hydraulic drive, and also includes extensive monitoring equipment. The purchase of such a device therefore requires a significant investment, which is difficult in a very cost sensitive activity as the stripping of floor coverings. Moreover, the device described in WO 201 1/094719 A1 weighs more than 1366 kg (3000 lb), which in itself may already pose a problem for many load bearing surfaces in buildings.

Also, US 6988776 B1 and US 7093906 B1 describe a scraping machine specially designed for scraping off old carpet, tiles or other floor coverings. A complex electrical/hydraulic system provides for the drive of the two driving wheels at the rear, and for positioning of the scraping knife. An additional hydraulic motor may be provided in order to adapt the machine for grinding rather than scraping. Despite this possible additional function of this scraping machine, the proposal from these documents remains very complex, and thus represents a large investment for a yet rather limited use.

There therefore remains a need for a simpler solution to remove coverings from horizontal surfaces, such as with floors and roofs, which in particular does not require high investments, but yet is faster and/or requires less labour time than the manual removal of the coverings. US 2007/0228805 A1 discloses a single-axis electrical tractor, such as available from the firm NuStar from Shakopee, Minnesota (USA), on which on the front side by means of a mounting piece in a removable manner a conventional electrically-driven thrust hammer has been attached, such as obtainable from the company Metabo from Germany. The impact angle A which the blade of the thrust hammer makes with the floor to be treated, may be set step-by-step by running the bolts, which are holding the thrust hammer screwed down, through another opening in the mounting piece. The centre of gravity of the entire device is located in front of the axle of the tractor, so that the knife of the thrust hammer is carrying part of the weight, which ensures that the knife is constantly being pulled by gravity towards the floor to be treated. According to the document, the device may be used for breaking up concrete floors, and for removing ceramic tiles or asphalt, but also linoleum and wooden floors, and makes such tasks less physically demanding and labour intensive compared to the manual activity. The thrust hammer may be detached from the tractor so that it may be used for handheld use at corners and edges which are difficult to access for the entity including the tractor. The single-axle tractor, according to US 2007/0228805 A1 has no other function, so that its acquisition still requires considerable investment with a rather limited usefulness with the stripping of buildings.

US 6957869 B1 and US 2003/0084920 A1 describe a possibility to attach a scraping knife to the bottom plate of a loading bucket of a bulldozer with front loader, to remove in this way road markings, reflectors and marker buttons from hard surfaces such as asphalt or concrete motorway surfaces. In US 6957869 B1 the scraping knife may be preceded by heat radiators in order to soften thermoplastic adhesives or bitumen, in order to thereby facilitate the peeling off of the tape or to soften the bitumen with which some objects may be fixed to the road surface. The arrangement has the advantage that the scraped objects mainly end up in the loading bucket of the front loader, so that they may be disposed of promptly and safely without having to be picked up. In US 6957869 B1 and US 2003/0084920 A1 , the scraping knife is screwed down with bolts to the loading bucket, so that a precisely flat underground of a road surface is necessary in order to function well and to maintain a good contact of the blade with the road surface. The proposal in these documents is also intended for road works outdoors and uses the large front loaders which are common therewith, and which are far too large for working indoors, in tight spaces and with narrow passages.

US 3563608 describes a tool to be mounted by means of four bolts and a coupling plate onto the front of the nose of a two- axle tractor, which leads via a rigid structure into a series of long, sloped teeth with bevelled point. The tool is meant, driven by the tractor and in the manner of a snow plough, with the tips of the teeth to break the link between old roofing paper and a roof in several places and to subsequently push the roofing paper upwards over the teeth of the accessory piece. The disadvantage of the device from US 3563608 is that its proper functioning requires an exactly flat surface. When one of the wheels of the tractor would ride over a bump, this will alter the position of the teeth, and this will then deviate from the horizontal line which is necessary to keep the contact with the surface to be scraped. Thereby, the covering will in certain places only partially or not at all be scraped off, or one runs the risk that the teeth penetrate the surface and seriously damage it.

JP 2006291592 discloses a scraping machine, which is detachably mountable on the movable blade of an excavator. A hydraulic motor provides for a forward and backward reciprocating movement which, via a curved transmission element is transmitted to the scraping knife. The machine described herein is rather complex and requires its own hydraulic drive system, which has an adverse impact on the cost of such a machine. Due to the reciprocating movement of the scraping knife, and this at an angle Θ with the floor line, the contact of the blade with the floor line is also not continuously assured. Thus it remains possible that traces of glue, cement, or any other substance with which the floor covering is attached to the substrate remain on the scraped surface.

JP 2005207183 discloses a scraping machine which is designed to scrape covering material from a floor, wall or ceiling. The scraping machine is rotatably mountable on the end of an arm of an excavator and is hydraulically driven. The hydraulic motor is fed with hydraulic oil from the excavator. The motor passes a vibrating movement onto a knife holder at the end of a front and curved axle, with in the knife holder a scraping blade releasably provided for scraping the covering material from a surface. Also this machine is rather complex and requires a hydraulic drive system, which has an adverse impact on the cost of such a machine. ^' Furthermore, the engine of the scraping machine is to be hydraulically coupled to the hydraulic system of the excavator when installing the scrape machine on the excavator.

JP 2007-016409 discloses a scraping machine, for the scraping off of insulation foam, which is mountable onto the movable arm of an excavator. The scraping machine comprises a chassis provided with two air valves and an oscillator, which is connected with a basket. At a forward and backward oscillation of the basket, driven by the oscillator, the scraping blade, which is mounted onto the end of the basket, digs into the insulating material. Saw blades provided on the sides of the basket cut the insulation in large chunks and ensure that as little as possible chlorofluorocarbons (CFCs), which are encapsulated in the foam, are released. Such a machine is limited in terms of applications because it is in the first place provided for scraping insulation foam from walls and ceilings, and it is not particularly suitable for the efficient removal of a floor covering. Also, this scraping machine is relatively complex because the movement of the basket is to be driven.

Thus, there remains a need for a simple manner to remove, with minimal additional resources on top of the standard equipment of an entrepreneur who specializes in stripping buildings for renovation, in a fast way with high precision the coverings of floors and/or roofs.

The present invention has for its object to avoid or at least alleviate the problems described above, and/or generally to provide in improvements. SUMMARY OF THE INVENTION

According to the invention, a coupling piece is provided, the coupling piece together with a scraping knife, an assembly of a standard bulldozer for indoor work, which is provided with an approximately vertical planer and/or a hoisting crane, with thereon the coupling piece mounted together with the scraping knife, and a method for the scraping of coverings of approximately horizontally level surfaces, such as floors and/or ceilings, which makes use of the assembly with the standard bulldozer as defined in any of the claims appended hereto.

In the first place, the present invention provides a coupling piece which is suitable for the transmission of thrust forces between the coupled elements, which is provided with a means with which the coupling piece may removably be attached to a movable part of a bulldozer suitable for indoor work, and which is also provided with a means which is suitable for receiving in a removably and rotatable manner the round stem of a holder for a stabbing knife and wherein the coupling piece holds the stabbing knife holder.

In another embodiment, the present invention provides a method for removing a covering from a surface, preferably an approximately horizontal level surface such as a floor or a roof, by means of a stabbing knife in a holder with a round stem which is, by means of the coupling piece according to the present invention, rotatably attached to a moving part of a bulldozer suitable for indoors work, and in which the stabbing knife is driven by the bulldozer.

The applicants have found that the coupling piece of the present invention makes it possible to remove coverings of floors and/or roofs by deploying as many elements as possible of the standard equipment of an entrepreneur who is professionally occupied with the stripping of buildings, and as such with a minimum of additional investment.

Thanks to the coupling piece according to the present invention, the covering of floors and/or roofs may be removed without having to bring in a specially designed machine. The mechanical removal of the floor- or roof coverings thus requires, thanks to the coupling piece according to the present invention, no additional transport of machines. The inventors have also found that the machines known in the art which are especially designed for scraping off of floor or roof coverings, are characterized by a relatively high weight, and because of their drive on wheels also by a relatively high point load. The machine described in WO 201 1/094719 A1 weighs at least 3000 pounds (1366 kg).

These machines are often electrically powered, and carry large and rather heavy batteries. This creates the difficulty that not every building has an elevator which is able to bring such heavy machinery directly to the appropriate floor. In such a case it will be required to remove for example the batteries temporarily from the machine, in order to reduce the weight of the machine and yet to be able to use the available elevator. The batteries must be brought up separately and be remounted into the machine before the machine may be movable on its own, let alone be useful for the stripping of floor covering. Or one is forced to hoist the machine with a mobile crane to the desired floor. Both options represent a loss of time and/or additional costs, which may be avoided thanks to the coupling piece of the present invention.

The coupling piece according to the present invention holds the stabbing knife holder. The means which is suitable for receiving in a removable and rotatable manner the round stem of a holder for a stabbing knife is thus integrated into the coupling piece, and forms an integral part of the coupling piece. This allows transferring the forces directly and with more precision from the coupling piece to the stabbing knife. Consequently, the coupling piece allows for the cutting blade of the stabbing knife to continue maintaining the best possible contact with the surface to be scraped, so that the work is carried out more thoroughly than with the embodiments according to the state of the art, and with less risk for damage to the substrate by penetration of the stabbing knife. Moreover, such a tool is much easier to execute than the embodiments according to the state of the art, and the simple construction with few moving parts, requires less maintenance and reduces the risk for damage to the components. The coupling thus allows operating with higher precision so that the stabbing work is more effective in the removal of the covering, and that the stabbing work also removes no more than the covering and its adhesive layer. The higher precision and direct transmission of forces from the coupling piece to the stabbing knife also ensure that the scraping runs less jerky and that therefore less dust and/or hazardous substances are released and also the associated vibrations are less. Both contribute to a better environment, safety and hygiene in the workplace.

An additional advantage of the coupling piece according to the present invention is its simplicity. Indeed, the coupling piece itself holds the stabbing knife with the means which is appropriate for that and which is fully integrated into the coupling piece. The coupling piece comprises no motor or any other means of driving in order to confer a forward/backward reciprocating movement or vibration to the stabbing knife, such as the more complex embodiments known from some of the documents discussed above. This means that the coupling piece is simple to manufacture, easy to transport, to install and to take back Off, and needs no additional connection for powering any drive.

An additional advantage of the coupling piece according to the present invention is that the operator may proceed with the same bulldozer suitable for indoor work which he or she also uses for many other tasks, and which he thus has a lot of experience with and therefore is able to readily and precisely handle. The inventors have experienced that the machines known in the art, which are specially designed for the scraping of floor or roof coverings, and of which a few have already been mentioned above, are characterized by a very sensitive and nervous manoeuvring behaviour. It thus requires a long apprenticeship before the operator is able to handle it with sufficient ease and precision. However, because these machines can only be used for their special stripping function, , there are only limited opportunities and time periods for gaining experience with these machines. The learning curve with the specially designed machines is hence less steep and has many long interruptions, because of which a part of the accumulated experience is lost again. It takes a long time before an operator achieves the same fluency and precision with the specially designed machines as compared to the level he achieves very quickly with the bulldozer which he also uses for all other activities. The coupling piece according to the present invention avoids this problem.

In addition, the coupling piece according to the present invention allows removing such coverings much faster than what is typically possible with a purely manual process, and furthermore, the physical effort demanded from the performers of the work remains relatively limited. The manual stripping of floor or roof coverings is after all, because of the many bending, pulling and dragging, rather stressful for the workers, especially taxing on the back. Manual floor stripping is therefore an activity which the same person may only sustain for a limited period of time. Machine stripping may be sustained much longer without problems. The advantage of machine stripping, which is made even more easy with the coupling piece according to the present invention, therefore also manifests itself in the fact that a smaller team may manage the same project in a much shorter period of time.

The inventors have also found that in some cases the covering was really not removable manually in an acceptable period of time, but that a machine removal was still workable. An example of such difficult covering was a carpet which had been very firmly glued on top of a glued linoleum substrate. A manual approach was unacceptable in terms of time and human effort, but the bulldozer with the coupling piece according to the present invention yet got the job done.

With respect to the present invention, the term "thrust knife" is also used now arid then. By that term is meant the combination of the stabbing knife holder with the stabbing knife. The blade of the thrust knife is the same as the blade of stabbing knife. Where is stated that the coupling piece holds the thrust knife, is therefore meant that the coupling piece holds the stabbing knife holder which in turn holds the stabbing knife.

The coupling piece according to the present invention holds the thrust knife in a manner which allows a rotation of the thrust knife around an axis which is approximately perpendicular to the cutting of the blade of the thrust knife. As a result, the coupling piece allows that the cutting blade of the thrust knife continues to maintain the best possible contact with the underground to be scraped, so that the work is carried out more thoroughly than with the embodiments according to the state of the art, and with less risk to damage the underground by penetration of the thrust knife. The coupling thus allows operating with higher precision so that the stabbing work is more efficient in the removal of the covering, and also does not remove more than the covering and its adhesive layer. With the coupling piece according to the present invention, there is therefore less need to pass more than once over the same surface in order to remove those pieces of the covering which remained stuck during the first passage because the knife could not maintain a good contact with the substrate.

The higher precision which is possible in the work with the coupling piece according to the present invention has other advantages, especially when compared to a manual removal. Thus, there is a better separation achieved between the covering, including its adhesive layer, and the substrate. After the removal of the covering, the underlying substrate must be levelled all over again before a new covering may be applied. A better removal of the adhesive layer also makes it possible to apply a much less thick levelling layer, for example, only 0.5 mm thick, instead of usually 2 mm thick, which saves raw materials, is logistically simpler, and which applied layer also much faster dries up. Especially in areas where one wants to start again an economic activity as quickly as possible, such as with the redecoration of existing retail spaces, a stripped floor which after equalization is drying faster means a significant time saving, and thus an important economic advantage.

The higher precision of the coupling piece according to the present invention may also entail other economic advantages. The waste from for example an old roofing covering is to be deposited as hazardous waste under many environmental legislations, which is complex and usually involves considerable additional administration and costs. With a careless removal, the underlying concrete is typically still quite polluted with pieces of roofing and bitumen, such that the disposing of the underlying concrete rubble must be paid for. If the roofing membrane and bitumen are removed with higher precision, only the disposal of the removed covering should be paid for and the concrete may usually be deposited for free as ordinary debris, or may even be crushed and reused if desired.

The knife in the device of WO 201 1/094719 A1 is mounted somewhat rotatably, around an upper pivot point which is indicated by number 36 in figure 1 , so that the knife is self-balancing. According to the explanation on page 12, lines 17-21 of WO 201 1/094719 A1 , this ensures that the desired contact between the scraping line of the knife and the floor surface is achieved when the blade is being lowered for use, even if the blade moves over waste which would lie on the floor surface. However, the axis through the pivot point is positioned much higher than the scraping knife, so that, while scraping, due to the leveraging effect of the resistance of the floor covering, and the friction with the trailing support plate, the blade is not able to rotate any longer. An additional disadvantage is that during any rotation of the blade around the indicated pivot point, the knife moves laterally relative to the floor which it must be scraping, which affects the precision of the delivered work. It is because of these reasons that the inventors prefer that the round stem of the stabbing knife holder which is used with the coupling piece according to the present invention is provided centrally with respect to the blade of the stabbing knife. In this way, the thrust forces are transmitted to the blade without seriously hindering or preventing the possibility for rotation of the knife and the stabbing knife holder with respect to the coupling piece, and therefore also of the bulldozer. SHORT DESCRIPTION OF THE DRAWINGS

Figure 1 shows a perspective top view of a coupling piece according to an embodiment of the present invention, which holds a stabbing knife holder with therein a stabbing knife.

Figure 2 shows a perspective view, taken from a rear side, of the coupling piece according to Figure 1 , including the stabbing knife holder and the stabbing knife.

Figure 3 shows a side plan view of a standard bulldozer suitable for indoor work, whereby a stabbing knife is attached to the planer blade of the bulldozer by means of the coupling piece according to Figures 1 and 2.

Figure 4 shows a side plan view of an accessory piece which is suitable attach the coupling piece according to figures 1 and 2 to the movable head of the hoisting crane of the bulldozer shown in Figure 3.

Figure 5 shows a perspective view, taken from the side at the front, of the accessory piece according to Figure 4.

DETAILED DESCRIPTION

The present invention will be described below, in certain embodiments, and with reference to certain drawings but the invention is not limited thereto, only by the claims. The drawings are only schematic and are non-limiting. In the drawings, some of the elements may be exaggeratedly shown and not drawn on scale for illustrative purposes. The dimensions, also relatively, in the drawings do therefore not necessarily correspond to how the invention is put into practice.

In addition, the terms, first, second, third, and so on, in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. These terms are interchangeable under appropriate circumstances and the embodiments of the invention may occur in sequences other than those described and illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and in the claims, are used for descriptive purposes and not necessarily to denote relative positions. The terms so used are mutually interchangeable under appropriate circumstances and the embodiments of the invention may occur in sequences other than those described and illustrated herein.

The term "comprising" as used in the claims, should not be construed as limiting to the elements that are listed in context with it. It does not exclude that other elements or steps occur. It must be regarded as prescribing the presence of the features, integers, steps or components as prescribed, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof.

Thus, the extent of "an object, comprising means A and B" can not be limited to an object which only consists of means A and B. It means that A and B are the only elements of interest for the object in connection with the present invention.

The applicants have found that most entrepreneurs, who are professionally occupied with renovating buildings, and certainly those who are professionally occupied with the stripping of buildings and the removal of floor and roofing materials, often use for these activities a small bulldozer suitable for interior work.

These bulldozers must be sufficiently small and agile to be suitable for indoors work. They have to be able to be used in small spaces, and also be able to move through relatively narrow openings, such as through door openings in load-bearing walls, in order to drive, for example, from one workspace to another. They also preferably have a weight which is not too high, so that mainly the point load they cause on the floor surfaces is kept within certain limits.

These bulldozers suitable for indoor work are preferably equipped with multiple tools, in order to be able to perform a wide range of tasks and functions with the same device or machine. In some embodiments, these bulldozers will be referred to as demolition robots, which may be controlled by remote control.

Therefore, they are usually provided with a planer in the front of the vehicle, of which at least the height may be changed and set, generally also the slope of the blade may be set, usually by means of one or more hydraulically driven rods. The planer may, for example, be used for collecting debris. The planer may be flat but is usually slightly bent or has crimped ends, at least at the top, so that with an accumulation of debris, pushed forwards by the planer, less of the accumulated debris ends up behind forwarding planer. The planer itself is not equipped with sharp sides, because these would wear rather quickly and become blunt. The planer is itself not suitable for scraping coverings of floors or roofs as a stabbing knife. A bulldozer for interior or indoors work is also usually equipped with a movable working arm, preferably at least in two sections, but sometimes three sectional, also called "the hoisting crane". This hoisting crane may usually be turned, often together with the entire superstructure of the bulldozer and positioned together on a kind of platform, around a vertical axis, so that the bulldozer with its hoisting crane may also reach to the left or right. A two-sectional working arm allows to independently choose both the height and the range of the reaches and thus offers an ample freedom of movement.

The hoisting crane is usually provided with a movable head. The head is usually rotatable around a fixed axis, attached to the end of the working arm and usually directed perpendicular to the plane in which the work arm may swing relative to the vertical axis around which the working arm is rotatable. The rotational position of the movable head around said axis is then typically set with hydraulic rods.

Typically a tool as desired may be attached to this movable head. This tool may then be brought in position by the working arm and the movable head and further be used to carry out tasks, both with respect to the distance from and the height relative to the bulldozer, as well as the rotational position relative to the end of the working arm. The tool is preferably attached to the movable head in such a way that it may be removed when it is not required, and possibly may be hindering, such as in planing activities. One tool may in that case be replaced by another tool. It is a preference to provide the tool in such a way, provided the tool is put in a particular position on the floor, that the tool may be picked solely by the movement of the bulldozer, the working arm, and the movable head. In that way there is need for only one person, for example, to exchange the tool at the head of the hoisting crane of the bulldozer with another tool. It may therefore be done by the operator of the bulldozer itself, without the help of a second person.

A common tool is a loading bucket or grapple, by which debris may be scooped Up but also heavier objects may be picked up and moved. Another very useful tool is a pick hammer or demolition hammer, in order to be able to break up or rework, for example, concrete or stone structures. These typically require an additional power transmission, such as a hydraulic connection with the bulldozer, usually via the working arm. Another tool is a bolt cutter or breaker, with which concrete may be cut into pieces.

Usually the bulldozer is even more powerful in the transmission of forces to the tool at the head of the hoisting crane when the bulldozer itself is stopped, as compared to with the planer, when the bulldozer itself is moving.

To the knowledge of the applicants, a stabbing knife to be attached to the head of a hoisting crane of a bulldozer suitable for indoor work is not yet available.

The applicants have felt a need to use this bulldozer, suitable for a wide range of interior activities, also for removing floor coverings, a sometimes time-consuming and labour-intensive activity in the stripping of buildings. The applicants have therefore devised the coupling piece according to the present invention and tested it with the method according to the present invention. The applicants have found that in this way, for example, a glued floor covering may quickly and without a lot of physical effort be scraped from a flat underground, and that this may be done very thoroughly in only a single pass because the blade is able to rotate with respect to the coupling piece. This allows the blade to retain contact with the substrate even if the substrate is not perfectly horizontal, especially with local deviations, or if the bulldozer has to drive over an uneven surface whereby the bulldozer is not perfectly upright.

In an embodiment, the means with which the coupling piece according to the present invention may be attached to a movable part of the bulldozer is a means for mounting the coupling piece on a blade which is part of a movable part of a bulldozer suitable for indoor work, such as, for example, the blade of the planer of the bulldozer, or a similar blade, for example, a blade which is provided as part of an accessory piece, which blade is provided for being attached to the movable head of the hoisting crane of the bulldozer. The applicants have found that in this way, the same coupling piece, which may be executed simple because it only needs to be able to be attached onto a blade which is flat or slightly bent or curved, may also serve to be attached in a different way to the bulldozer, whereby it may be used in several and different ways, and whereby the stabbing knife may be used for multiple and mutually different functions. The attachment to the planer of the bulldozer is suitable for the removal of an approximately horizontal floor or roof covering, whereby the bulldozer may move forward and, for example, a large area may be treated quickly. If, on the other hand the coupling piece is attached to the movable head of the hoisting crane of the bulldozer, then the stabbing knife becomes highly manoeuvrable in all directions and operational at all heights and against any kind of substrates. In this way, the stabbing knife may be used in places which it could not reach if the coupling piece is attached on the planer of the bulldozer. As such, the stabbing knife may also be used in corners and edges, under fixed objects such as central heating radiators, in narrow spaces which would be inaccessible for the bulldozer itself and on elevations such as steps of a staircase or on consoles. Moreover, the angle of the stabbing knife with the floor surface on which the bulldozer sits is thereby substantially completely freely adjustable, so that the stabbing knife may also be used for the removal of coverings from vertical surfaces, or from surfaces under any angle of inclination, even from ceilings.

An additional advantage of being able to attach the coupling piece, and therefore the stabbing knife holder with the stabbing knife, to the planer of the bulldozer, is that the coupling piece may also be placed in a non-central position with respect to the planer, such as at one of the outer edges. In this way, the stabbing knife may protrude laterally with respect to the direction of movement of the bulldozer itself, so that it may reach surfaces which are not accessible by the planer, such as, for example, under the central heating radiators, or other types of objects or protrusions which are preferably not removed for the stripping of the space and/or the removal of the covering.

The coupling piece according to the present invention must be suitable to transfer thrust forces between the coupled elements, i.e. the thrust forces which are required for with the stabbing knife removing various kinds of coverings from surfaces. The coupling piece itself must be fairly sturdy, and be manufactured from a strong material. The applicants prefer to manufacture the coupling piece from carbon steel, also known as structural steel, but other materials having about the same or better relevant mechanical properties are equally suitable.

In an embodiment according to the present invention, the blade on which the coupling piece may be attached is the blade of the planer of the bulldozer, also known as the planer blade. Such a planer blade has specific movement possibilities with respect to the bulldozer, which, although being somewhat limited, still allow the correctly positioning of the stabbing knife via the coupling piece for scraping off a floor or roof covering. The planer of the bulldozer has the advantage that this is usually the movable part of the bulldozer with which the strongest forces may be transmitted.

In an embodiment according to the present invention, the means for mounting the coupling piece onto the blade comprises a fixed collar in order to grip around one of the sides of the blade, preferably one of the long sides, more preferably the underside of the blade. Such a collar may be compact and readily made from the same material as the coupling piece, and preferably forms part of the coupling piece. Providing the collar simply as a part of the coupling piece keeps the coupling piece simple in construction and thus keeps the manufacturing easy and quick, so that one has to call upon limited special techniques and components in the manufacture thereof. Because the collar is also compact, the coupling piece in the mounted condition represents only a small obstruction in the freedom of movement of the blade onto which the coupling piece is mounted. The applicants place the collar preferably on one of the long sides of the blade, because in that way the coupling piece may be more compact. By letting the collar grip around the underside of the blade and further letting the coupling piece rest against the blade, one obtains the advantage that the blade may transmit in addition to the thrust force also a downward force to the coupling piece and thus to the stabbing knife, without any additional aid. In an embodiment according to the present invention, the means for mounting the coupling piece on the blade comprises a clamp in order to be clamped around one of the sides of the blade, preferably one of the long sides, more preferably the upper side of the blade. By use of a clamp, a fixed and immovable attachment of the coupling piece on the blade is created, whereby forces and movements may be transferred from the blade to the coupling piece, and thus to the stabbing knife, in all directions. The applicants preferably use the clamp together with the collar as described above, in such a way as to allow the coupling piece to grip around the blade on two sides, preferably on two long sides, even more preferably two opposite long sides. In this way, the coupling piece may be attached to the blade in a very firm way, so that strong forces may be transferred from the blade to the coupling piece and thus also to the stabbing knife, in all directions. This allows using the coupling piece with coverings which are very firmly attached to their substrate.

In the embodiment according to the present invention wherein the clamp is fixed on the side of the blade, the applicants preferably provide the clamp with a closing plate which grips around the edge of the blade, whereby preferably at least one, and more preferably at least two bolts protrude through the closing plate, and wherein at least one bolt and preferably each bolt after the fastening of the clamp is held under tension by a spring washer or resilient ring. Preferably applicants use hexagon headed bolts. The bolts are preferably provided with a part with a screw thread, either on which a nut may be screwed, or with which the bolt may be screwed in an opening of the coupling piece which has the fitting diameter and in which a suitable screw thread is provided. The applicants have found that thereby a firm clamp may be provided as part of the coupling piece in a simple way, and which may also simply and securely be tightened with simple tools such as an open ended or a ring spanner of the appropriate size, which is part of most standard toolboxes. The closing plate according to the invention is preferably executed in the same material as the coupling piece itself, and even more preferably with about the same thickness. In this way, one obtains a clamp which is sufficiently strong to keep the coupling piece firmly in place so that the scraping work may be performed with the desired precision, and which may also transfer the sometimes high thrust forces which may be needed in order to remove strongly attached coverings.

In the embodiment according to the present invention with the closing plate, the applicants preferably provide that the closing plate may still move or shift in one direction relative to the coupling piece, preferably because at least one of the apertures in the closing plate and/or the coupling piece allowing a bolt to pass, preferably all such apertures, is provided as an elongated opening, preferably an oval-shaped aperture. The direction of movement of the closing plate is preferably the direction in which the closing plate may grip farther or less far behind the blade. It is therefore possible to grip with the same coupling piece blades of different sizes. A similar coupling piece is therefore suitable to be mounted on, for example, bulldozers of different types or of different origins, of which the planer blades do not necessarily have the same dimensions or the same design. Such a coupling piece has the advantage that it may be deployed with a wider range of bulldozers suitable for indoor work.

In the embodiment according to the present invention with the closing plate, the applicants preferably provide that the closing plate is provided with individual lips in order to grip behind the blade, and wherein between the lips room is left for letting pass through the blade one or several rods, which attach the blade to the undercarriage of the bulldozer and possibly if so desired are able to change the position thereof relative to the bulldozer. Especially for the planer blades, but also for other movable parts of the bulldozers suitable for indoor work, the position of the blade may be changed. The planer blades are usually adjustable in height, and also the slope of the planer blade with respect to the horizontal plane may be adjustable. These movements are usually made by means of one or more rods, usually hydraulically driven in order to be able to manage strong forces. These rods are typically mounted with pivot points at the back of the blade or the part of which the blade forms a part. The attachment points of these rods are usually apart as far as possible in order to obtain the highest possible leveraging effect. By providing the closing plate of the coupling piece according to the present invention with individual lips with in between room for the rods, the coupling piece may also be attached at the most suitable location of the blade, i.e. the location at the front of the blade where at the back the rods are attached which hold the blade and with which the position of the blade may be changed. In this way, it is prevented that additional leveraging effects emerge or that such leveraging effects are kept to a minimum with the transmission of the forces from the blade, via the coupling piece, to the stabbing knife.

In another embodiment according to the present invention, the coupling piece is provided with a means by which the coupling piece may be attached to the movable head of the hoisting crane of a bulldozer suitable for indoor work. This brings the advantage that the stabbing knife is highly manoeuvrable in all directions, and/or may be used with greater force and/or higher precision. In this way, the stabbing knife may be used in places it would not be able to reach if the coupling piece would be mounted on the planer of the bulldozer. Thereby, the stabbing knife may also be used in corners and edges, in narrow spaces which are inaccessible to the bulldozer itself, or under protrusions such as central heating radiators, and elevations such as steps of a staircase or on consoles. Moreover, the angle of the stabbing knife with a horizontal plane is thereby substantially completely freely adjustable, so that the stabbing knife may also be used for the removal of coverings of vertical surfaces, or of surfaces under any angle of inclination, even from ceilings. Preferably, this means comprises an accessory piece. In this way, the coupling piece may be kept of simple and light design, so that it is convenient in mounting on and removal from the bulldozer. The accessory piece as such may also be of simple and light design, and must only be applied and used with tasks which are better performed with the stabbing knife onto the working arm of the bulldozer instead of on the planer blade.

In the embodiment of the present invention, wherein the coupling piece is provided with a means to attach the coupling piece to the movable head of the hoisting crane of a bulldozer intended for indoor work; the applicants preferably provide that the means to attach the coupling piece to the movable head of the hoisting crane comprises at least one grip handle, preferably two grip handles, suitable for each grasping around a round axis which is provided as a protrusion on the movable head of the hoisting crane, and around which the coupling piece is rotatable with respect to the head of the hoisting crane. This offers the advantage of a greater mobility of the coupling piece, and thus of the stabbing knife which is held by it, with respect to the head of the hoisting crane. This makes the assembly of bulldozer, coupling piece and stabbing knife better and more readily usable for more and different tasks, also with a higher degree of difficulty.

In the embodiment according to the present invention, wherein the means to attach the coupling piece to the movable head of the hoisting crane comprises an axis around which the coupling piece is rotatable with respect to the head of the hoisting crane, the applicants preferably provide that the means to attach the coupling piece to the movable head of the hoisting crane further comprises at least one stop and preferably two stops, suitable for, during the movement of the head of the hoisting crane, also taking along the coupling piece in that movement. This offers the advantage that the position of the coupling piece, with respect to the movable head of the hoisting crane, may be limited in at least one direction of rotation around the axis. As a result, forces may be transferred, at least in one direction of rotation around this axis, but which may already be sufficient for performing particular tasks with the stabbing knife.

In an embodiment according to the present invention, the means to attach the coupling piece to the movable head of the crane further comprises at least one cam, and preferably two cams, suitable for receiving a removable anchor which is suitable to anchor the position of the coupling piece relative to the movable head of the hoisting crane. This allows anchoring the position of the coupling piece, and thus the stabbing knife, with respect to the movable head of the hoisting crane. As a result, the movement of the stabbing knife with respect to the bulldozer may be controlled even more, and, if desired, forces may be transferred in different directions from the working arm of the bulldozer to the stabbing knife, so that a wider variety of tasks may be performed. In an embodiment of the present invention, the coupling piece is further provided with a stabbing knife holder with a round stem, whereby preferably in the stabbing knife holder a stabbing knife is fixed, and wherein preferably the round stem of the stabbing knife holder is provided centrally with respect to the blade of the stabbing knife. Thus, the present invention also provides in an assembly of the coupling piece with a stabbing knife holder which has a round stem. In that stabbing knife holder may then be fixed an appropriate stabbing knife. Suitable stabbing knife holders with round stem, and matching knives in all shapes and embodiments, are commercially available, for example, from the firm Unisteam - Rovako in Belgium or Behrends Bodentechnik in Germany.

In one embodiment of the present invention the means to be able to receive the round stem of the stabbing knife holder is a cylinder-shaped receiver. The applicants preferably obtain in this way that the stabbing knife may receive in a removable and rotatable manner the round stem of a stabbing knife. The thrust forces may then, for example, be transferred, by a contact provided between the end of the stem of the stabbing knife and a part of the coupling piece, for example the back of it. In this way, the rotation of the stabbing knife in relation to the coupling piece is not or hardly hindered, so that the precision of the stabbing work is not or hardly jeopardised. An additional advantage is that the cylindrical shape is much easier to manufacture than the possible alternatives, because the cylindrical receiver may be cut from a tube having the appropriate diameter, and the round stem which must fit into it from a rod having the appropriate diameter.

In the embodiment of the assembly of the coupling piece with the cylinder-shaped receiver, the applicants preferably provide that the round stem of the stabbing knife is provided with a thrust collar, wherein the cylinder-shaped receiver is suitable to fit against the thrust collar of the stabbing knife and to thereby transmit the thrust forces. The applicants have found that in this way stronger forces may be transmitted to the stabbing knife without jeopardizing the rotatability of the stabbing knife relative to the coupling piece. In this way, also the desired precision of the scraping task to be performed may be maintained as good as possible.

In the embodiment of the assembly of the coupling piece with the stabbing knife holder with a round central stem, the applicants provide preferably that the round stem of the holder of the stabbing knife is provided with a means suitable for receiving a removable element, such as an opening for a split pin, and whereby the element has to be removed before the holder of the stabbing knife may be removed from the coupling piece. In this way, the stabbing knife may be secured or anchored in the coupling piece via its holder, and this without jeopardising the rotatability, so that the knife may not drop or slide out of the holder at an undesired moment. This is particularly convenient in those embodiments wherein the coupling piece with a stabbing knife has a high freedom of movement in various directions. Preferably the applicants provide that this removable element and the coupling piece are such that the presence of the removable element only permits a small movement or no movement at all, of the stabbing knife in the direction of thrust. In this way, the stabbing knife may also, be brought in position in a downward direction with great precision. This enhances the speed and precision of the scraping work, primarily with such difficult tasks.

In an embodiment, the present invention provides a bulldozer suitable for indoor works with the coupling piece according to the present invention mounted on one of its moving parts. Thus, the present invention also provides an assembly of a bulldozer suitable for use indoor tasks with the coupling piece according to the present invention. The assembly according to the present invention preferably also comprises the stabbing knife with a round stem. Suitable bulldozers are available commercially, for example the types Husqvarna DXR 310 or 250, or the yet lighter DXR 140 which weighs less than 1000 kg, obtainable from the firms belonging to the Husqvarna Group, such as Husqvarna Construction Products. Also the type Tb 108 of the firm Takeuchi was found to be quite suitable. Suitable machines may also be found in the offerings of the firms Yanmar or Mecalac, distributed in Belgium by Cebeko, or of Atlas Copco, or among the models from the KX series of the firm Kubota Tractor Corporation, for example, the model K008-3 or in the offerings of mini excavators by the Company JCB (U.S.), such as the model 8008 CTS with an operational weight of only 2094 pounds (950 kg).

In an embodiment of the assembly according to the present invention, the coupling piece is attached to the planer, or one of the planer blades of the bulldozer, or on a blade or planer which is attached as a tool to the movable head of the hoisting crane of the bulldozer. These modes of attachment offer the advantages which have already been mentioned above in connection with the features which allow the attachment or the mounting of the coupling piece to the bulldozer at these locations.

In an embodiment of the assembly according to the present invention, the coupling piece is attached as a tool on the movable head of the hoisting crane, preferably by means of an accessory piece. The advantages of this embodiment have also been discussed above in connection with the characteristics which allow the coupling piece to be attached to the bulldozer in this place and manner. The inventors preferably use an accessory piece for attachment to the head of the hoisting crane, because in this way, the coupling piece may be kept simple and remains lightweight. It is therefore simpler to manufacture, hence cheaper. Because of its limited weight, it is also more convenient and easier to transport, to mount onto and remove from the bulldozer. The accessory piece may then also be kept simple and light, so that it also remains very easy to handle.

In an embodiment of the assembly according to the present invention, the bulldozer runs preferably on caterpillar tracks. This mode of motion brings the advantage of a high grip on the surface without exerting a high point load on the substrate. Because the caterpillar tracks are usually controllable independently, this way of motion brings the advantage of a high manoeuvrability of the bulldozer, up to allowing even a so-called "zero turning radius", i.e. the ability to turn the bulldozer around a central vertical axis, without forward movement. The caterpillar tracks bring further benefits. For example, a bulldozer on caterpillar tracks manages much easier obstacles, obstacles which may be much higher than a wheeled machine is able to handle. Caterpillar tracks remain less readily stuck in pits and grooves. A bulldozer on caterpillar tracks may even climb stairs, which is much more difficult and often impossible for a machine wheels.

In the embodiment of the assembly according to the present invention with the bulldozer running on caterpillar tracks, the applicants provide preferably that the caterpillar tracks may be retracted laterally, preferably until the caterpillar tracks may pass through an opening of at most 90 cm wide, more preferably at most 80 cm wide, and even more preferably at most 70 cm wide. This brings the advantage that the bulldozer may move more freely through restricted passage ways, e.g. doorways, allowing it to access hard to reach places for carrying out scraping work, so that also in these places the covering may be removed quickly and with little physical effort.

In the embodiment of the assembly according to the present invention with the bulldozer, applicants prefer that the assembly gives a point load on its work floor, substrate or underground of at most 1000 kPa, preferably at most 950 kPa, more preferably at most 900 kPa, even more preferably at most 700 kPa, preferably at most 500 kPa, more preferably at most 300 kPa, even more preferably at most 200 kPa, preferably at most 150 kPa, more preferably at most 100 kPa, still preferably at most 95 kPa, preferably at most 90 kPa, more preferably at most 70 kPa, still more preferably at most 50 kPa, preferably at most 30 kPa, more preferably at most 25 kPa. This brings the advantage that the assembly may be used on floors which have only a limited load bearing capacity, so that also in these locations the covering need not be removed manually, but with the aid of the bulldozer suitable for indoor work may be removed quickly and with little physical efforts and burden for the personnel.

The coupling piece according to the present invention may thus also bring the advantage of a reduced point load. The Machine Stripper Ride-on-AII-Day Battery offered by the firm Unisteam - Rovako in Belgium, and Behrends Bodentechnik in Germany, and which is specially designed and intended for the removal of coverings has a point load at standstill of 10 kg force /cm², which corresponds to 98.1 Newton per cm², or 981000 Newton per m² or Pascal, and thus 981 kPa. A standard small bulldozer suitable for indoor work, on the contrary, such as the device of the type of the firm Takeuchi Tb 108, causes a ground pressure of only 22.4 kPa, which is almost 44 times lower. Thanks to the coupling piece according to the present invention a floor or roof covering may be mechanically removed from surfaces which are resistant to only a much lower point load. The coupling piece thus also offers the advantage that a covering may also be mechanically removed from these weaker structures, and that this task not necessarily needs to be done manually. This advantage is even clearer if a standard bulldozer is used which runs on electricity from the grid, because the weight gain increases further because also no batteries are needed. Also a bulldozer driven by a diesel engine is usually lighter than a machine which runs on batteries.

In the embodiment of the assembly according to the present invention with the bulldozer, the bulldozer is preferably electrically powered. The bulldozer then preferably does not comprise any internal combustion engines, and therefore produces no emissions during operation. The bulldozer then also produces less noise during operation. This brings the advantage that the use of the bulldozer for removing coverings may occur in closed rooms, and/or with a greater ease of use and user friendliness, such as with less inconvenience to the staff which is involved in the work. In another embodiment the bulldozer may be remotely operated, ideally wirelessly, so the staff is not or less exposed to the potentially harmful environment which may be caused by the stripping and demolition work.

In the embodiment of the assembly according to the present invention in which the bulldozer is electrically powered, the applicants preferably provide that the bulldozer may extract the energy for its drift from batteries which form part of the bulldozer itself. This brings the advantage that the bulldozer may execute its work autonomously, without any power cable to supply the energy for its drive. This gives the bulldozer greater manoeuvrability and makes the bulldozer usable in places and construction sites where a connection with the power grid is difficult or impossible to achieve.

In an embodiment of the method according to the present invention, the method makes use of the assembly of the bulldozer with the coupling piece according to the present invention, together with the stabbing knife and the stabbing knife holder.

In one embodiment of the method according to the present invention, the coupling piece is attached to the blade of the planer of the bulldozer, and the method comprises the step of advancing the bulldozer over the surface. The inventors have found that, for the stripping of most of the coverings, the force by which the bulldozer moves over an approximately horizontal plane is sufficient. The advantage here is that the stripping of the floor may occur with a relatively high speed, and yet may be done very precisely. The covering may in this manner be removed smoothly and properly, which is very beneficial for all parties involved in the task. In this embodiment, the method according to the present invention preferably also comprises the step, before the removal of the covering, of attaching the coupling piece to the blade of a planer of the bulldozer, by placing the collar around one side of the blade and positioning the closing plate of the clamp, and to tighten this clamp. The method preferably also comprises the step of inserting a suitable stabbing knife holder in the coupling piece, and to anchor it, if possible. The stabbing knife holder preferably already holds the stabbing knife. Alternatively, the stabbing knife is applied into the holder as an additional step of the method.

In the embodiment of the method according to the present invention, wherein the coupling piece is attached as a tool to the movable head of the hoisting crane of the bulldozer, or to the blade of an accessory piece which is attached as a tool to the movable head of the hoisting crane, for the removal of the covering from a small and/or hard to reach approximately horizontal plane, such as a step of a stairway or a console, or from a non-horizontally-lying plane such as a separation, a wall or a ceiling, wherein the method comprises the step of driving the stabbing knife by moving the head of the hoisting crane, optionally by the movement of the support rod of the hoisting crane in order to change the position of the knife in relation to the head of the crane. This brings the advantage that these coverings do not have to be removed manually, but may be removed quickly and with little physical effort by using the bulldozer suitable for indoor work. An additional element for preferring this method is that the forces which may be transferred by the working arm of the bulldozer are even stronger than those transferred by the forward movement of the bulldozer. So, if stronger forces are needed, one may preferably operate the stabbing knife through the working arm of the bulldozer. The downside is that it is very difficult to also forward the bulldozer during such work. In order to keep the operation practically possible, or to achieve or maintain the desired precision, the bulldozer will usually be kept stable and in the same place when operating the stabbing knife through the working arm, and the stabbing be interrupt when one wants the bulldozer to take up a new position. This way of working is usually a bit slower than when the knife is pushed forward as described above via the planer blade in front of the bulldozer. In this embodiment, the method preferably comprises the step of attaching an accessory piece to the movable head of the hoisting crane, for example by letting the grip handle(s) of the accessory piece grasp around an axis provided on the movable head. The method preferably also comprises the step of bringing the stop of the accessory piece to a position wherein it rests against an appropriate cam or protrusion on the movable head, preferably by making use of the force of gravity and the possibility of hydraulically moving the head. Preferably, the method also includes the step of anchoring the accessory piece to the movable head, so that it may be moved in all directions together with the movable head of the hoisting crane! Preferably only then, therefore, is the coupling piece according to the present invention attached to the accessory piece, in the manner as described above. If the stabbing knife holder and/or the stabbing knife have not yet been attached, it may be done subsequently as part of the process.

The method according to the present invention may further comprise the steps of removing, after the removal of the covering, the stabbing knife, the stabbing knife holder, the coupling piece, and where appropriate, also the accessory piece, from the movable part of the bulldozer suitable for indoor work. The method may then further comprise the step, if desired using a different tool, of carrying out a different task with the same bulldozer which has been employed for the removal of covering.

The invention is now further illustrated by the detailed description of one or more particular embodiments. The invention is not, however, limited to these particular embodiments. In the figures the same elements are indicated by the same reference numbers.

Figure 1 shows a perspective top view of a coupling piece 1 according to an embodiment of the present invention, which holds a stabbing knife holder 26 with therein a stabbing knife 25. Figure 1 shows in more detail the means 3 which is adapted to removably and rotatably receive the round stem 27 of the stabbing knife holder. The means 3 has a cylinder shape, which fits against a thrust collar 28 which is provided on the round stem 27 of the stabbing knife holder. The coupling piece 1 is further provided with a means 2 by which the coupling piece may be removably attached to a movable part of a bulldozer for indoor work. The means 2 consists of a sleeve 4 and a clamp 5. The clamp 5 is operated by bolts 7. Further to be seen on Figure 1 is an opening 29 which is provided in the round stem 27 of the stabbing knife holder 26. The opening 29 is suitable for receiving an element, such as a split pin (not shown) which may be passed through the opening 29. This element has to be removed before the stabbing knife holder 26 may be removed from the coupling piece 1 .

Figure 2 shows a perspective view, taken from the rear side, of the coupling piece according to Figure 1 , including the stabbing knife holder and the stabbing knife. On this figure, the sleeve 4 and the clamp 5 are better visible, which are suitable for grasping each time around one of the sides of a working blade, such as the blade of a planer of the bulldozer. The sleeve 4 and the clamp 5 in this embodiment are provided for engaging around opposite sides of a working blade. The clamp 5 is further provided with a closing plate 6. The closing plate is fixed by means of two bolts 7 which protrude through the closing plate. Both bolts 7 are provided with resilient rings 8 which may hold the bolts under tension upon tightening. The closing plate 6 is further provided with oval apertures 9 through which the bolts 7 protrude, so that the closing plate may move relative to the coupling piece, by which the closure plate is easy to apply and may also be fixed on a blade of which the width is slightly smaller than for which the sleeve and the clamp of the coupling piece are designed. The closing plate 6 is further provided with lips 30, between which room is left, if desired, for letting pass through a rod, with which the blade may be operated onto which the coupling piece is attached.

Figure 3 shows a side plan view of a standard bulldozer 10 suitable for indoor work, whereby a stabbing knife is attached on the planer blade of the bulldozer by means of the coupling piece according to figures 1 and 2. On this figure it may be clearly seen how the sleeve 4 and clamp 5 with closure plate 6 of the coupling piece 1 grip around blade 12 of planer 1 1 , and still leave room in order to let rod 13 pass through, which holds and operates the planer 1 1. In this way, the coupling piece may push ahead the stabbing knife holder 26 with the stabbing knife 25 via the cylinder-shaped holder 3. Also shown is the hoisting crane 15, on the working arm of which a movable head 16 is mounted, which is movable by means of an auxiliary hydraulic rod 17.

Figure 4 shows a side plan view of an accessory piece 20 which is suitable for attaching the coupling piece 1 according to Figures 1 and 2 to the movable head 16 of the hoisting crane 15 of the bulldozer shown in Figure 3. Here, too, it may be seen how sleeve 4 and clamp 5 grip around blade 21 of the accessory piece. Also shown as part of accessory piece 20 are grip handles 22, a stop 23 and a cam 24 for the connection to the movable head of the crane.

Figure 5 shows a perspective view, taken from the side in the front, of the accessory piece 20, with blade 21 according to Figure 4. Still more clearly seen in this figure are the grip handles 22, 22', the stops 23, 23' and cams 24, 24 for attaching the accessory piece, and preferably for anchoring it, to the movable head 16 of the hoisting crane 15 of the bulldozer 10 shown in Figure 3.

Claims

1. A coupling piece (1 ) which is suitable for the transmission of thrust forces between the coupled elements, which is provided with a means (2) with which the coupling piece may removably be attached to a movable part of a bulldozer suitable for indoor work (10), and which is also provided with a means (3) which is suitable for receiving in a removable and rotatable manner the round stem (27) of a holder (26) for a stabbing knife (25), and wherein the coupling piece holds the stabbing knife holder.

2. The coupling piece according to claim 1 , wherein the means (2) with which the coupling piece may be attached to a movable part of the bulldozer is a means for mounting the coupling piece on a blade (12, 21 ) which blade is part of a movable part of a bulldozer suitable for indoor work, such as, for example, the blade (12) of the planer (1 1 ) of the bulldozer, or a similar blade, for example, a blade (21 ) which is provided as part of an accessory piece (20), which blade is provided for being attached to the movable head (16) of the hoisting crane (15) of the bulldozer.

3. The coupling piece according to claim 2 wherein the blade on which the coupling piece may be attached is the blade (12) of the planer (1 1) of the bulldozer.

4. The coupling piece according to claim 2 or 3 wherein the means for mounting the coupling piece on the blade comprises a fixed collar (4) in order to grip around one of the sides of the blade (12, 21 ), preferably one of the long sides, more preferably the underside of the blade.

5. The coupling piece according to any one of claims 2-4 wherein the means for mounting the coupling piece on the blade comprises a clamp (5) in order to be clamped around one of the sides of the blade (12, 21 ), preferably one of the long sides, more preferably the upper side of the blade.

6 The coupling piece according to claim 5 wherein the clamp is fixed on the side of the blade with a closing plate (6) which grips around the edge of the blade, whereby preferably at least one, and more preferably at least two bolts (7) protrude through the closing plate, and wherein at least one bolt and preferably each bolt after the fastening of the clamp is held under tension by a spring washer or resilient ring (8).

7. The coupling piece according to claim 6 wherein the closing plate (6) may still move in one direction relative to the coupling piece, preferably because at least one of the apertures (9) in the closing plate (6) and/or the coupling piece allowing a bolt to pass, preferably all such apertures, is provided as an elongated aperture, preferably an oval- shaped aperture.

8. The coupling piece according to claim 6 or 7, wherein the closing plate (6) is provided with individual lips (30) in order to grip behind the blade, and wherein between the lips room is left for letting pass through the blade one or several rods (13), which attach the blade to the undercarriage of the bulldozer and possibly if so desired are able to change the position thereof relative to the bulldozer.

9. The coupling piece according to any one of the preceding claims, wherein the means by which the coupling piece may be attached to a movable part of the bulldozer is a means to attach the coupling piece (1) to the movable head (16) of the hoisting crane (15) of a bulldozer suitable for indoor work, which means preferably comprises an accessory (20).

10. The coupling piece according to the preceding claim wherein the means to attach the coupling piece to the movable head of the hoisting crane comprises at least one grip handle (22) and preferably two grip handles (22, 22'), suitable for each grasping around a round axis which is provided as a protrusion on the movable head (16) of the hoisting crane (15) and around which the coupling piece is rotatable with respect to the head of the hoisting crane.

1 1. The coupling piece according to the preceding claim wherein the means to attach the coupling piece to the movable head of the hoisting crane further comprises at least one stop (23) and preferably two stops (23, 23'), suitable for, during the movement of the head of the hoisting crane, also taking along the coupling piece in that movement.

12. The coupling piece according to claim 10 or 1 1 wherein the means to attach the coupling piece to the head of the hoisting crane further comprises at least one cam (24) and preferably two cams (24, 24'), suitable for receiving a removable anchor which is suitable to anchor the position of the coupling piece relative to the movable head of the hoisting crane.

13. The coupling piece according to any one of the preceding claims, which is further provided with a stabbing knife holder (26) with a round stem (27), whereby preferably in the stabbing knife holder a stabbing knife (25) is fixed, and wherein preferably the round stem of the stabbing knife holder is provided centrally with respect to the blade of the stabbing knife.

14. The coupling piece according to any one of the preceding claims, wherein the means (3) to be able to receive the round stem (27) of a holder (26) for a stabbing knife (25) is a cylinder-shaped receiver.

15. The coupling piece according to the preceding claim wherein the stabbing knife holder is provided with a thrust collar (28) on its round stem (27), wherein the cylinder-shaped receiver (31) is suitable to fit against the thrust collar of the stabbing knife and thereby transmitting the thrust forces.

16. The coupling piece according to any one of claims 14-16 wherein the round stem (27) of the holder of the stabbing knife is provided with a means (29) suitable for receiving a removable element, such as an opening for a split pin, and whereby the element is to be removed before the holder (26) of the stabbing knife may be removed from the coupling piece (1 ).

17. A bulldozer (10) suitable for indoors work with the coupling piece (1 ) according to any one of the preceding claims attached to one of its moving parts.

18. The bulldozer according to the preceding claim, wherein the coupling piece is mounted on the planer (1 1 ) of the bulldozer, or on a planer which is mounted as a tool on the movable head (16) of the hoisting crane (15) of the bulldozer.

19. The bulldozer according to claim 17 or 8, wherein the coupling piece is attached as a tool to the movable head (16) of the hoisting crane (15), preferably with an accessory (20).

20. The bulldozer according to any one of claims 17-19 which is capable of moving on caterpillar tracks.

21. The bulldozer according to the preceding claim, of which the caterpillar tracks may be retracted laterally, preferably until the caterpillar tracks may pass through an opening of at most 90 cm wide, more preferably at most 80 cm wide, and even more preferably at most 70 cm wide.

22. The bulldozer according to any one of claims 17-21 which gives a point load on its working floor of not more than 1000 kPa, preferably at most 950 kPa, more preferably at most 900 kPa, even more preferably at most 700 kPa, preferably at most 500 kPa, more preferably at most 300 kPa, even more preferably at most 200 kPa, preferably at most 150 kPa, more preferably at most 100 kPa, more preferably with not more than 95 kPa, preferably not more than 90 kPa , more preferably at most 70 kPa, still more preferably at most 50 kPa, preferably at most 30 kPa, more preferably at most 25 kPa.

23. The bulldozer according to any one of claims 17-22 which is electrically powered.

24. The bulldozer according to the preceding claim which is able to extract the energy for its drift from batteries which are part of the bulldozer.

25. A method for removing a covering from a surface, preferably an approximately horizontal level surface such as a floor or a roof, by means of a stabbing knife (25) in a holder (26) with a round stem (27) which is, by means of the coupling piece (1) according to any one of claims 1-16, rotatably attached to a moving part of a bulldozer (10) suitable for indoors work, and in which the stabbing knife is driven by the bulldozer.

26. The method according to the preceding claim, which makes use of the bulldozer according to any one of claims 17-24.

27. The method according to claim 25 or 26, wherein the coupling piece (1 ) is connected to the blade (12) of the planer (1 1) of the bulldozer (10), and wherein the method comprises the step of the advancing movement of the bulldozer over the surface.

28. The method according to claim 25 or 26, wherein the coupling piece (1 ) is attached as a tool to the movable head (16) of the hoisting crane (15) of the bulldozer (10), or to the blade (21) of an accessory (20) which is attached as a tool to the movable head (16) of the hoisting crane (15), for the removal of the covering from a small and/or difficult to reach approximately horizontal surface, such as a step of a stairway or from a console, or from a non-horizontal surface such as a partition, a wall or a ceiling, the method comprising the step of driving the stabbing blade by moving the head (16) of the hoisting crane (15), optionally by the movement of the auxiliary bar of the hoisting crane in order to change the position of the knife in relation to the head of the hoisting crane.