ES1317457U - Safety system for the protection of a construction saw operator (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Safety system using artificial vision for the protection of the operator of a construction saw or similar machine tool in which the piece to be machined is fed manually by the machine operator, comprising the following elements: - A high-resolution, high frame rate, fixed-focus camera (1), connected to the processing unit and responsible for taking images in real time. - A processing unit (2), which analyzes the images received by the camera (1), determining by means of its model trained by artificial intelligence if there is a limb of the machine operator in an area delimited as dangerous (16). In the event that a dangerous situation exists and consequently occurs, a signal is sent instantaneously to the machine stop device (3). The processing unit (2) must have sufficient power to analyze the images received from the camera (1) in real time, execute the recognition model and act on the machine stop device (3), all instantaneously. - A machine stopping device (3), responsible for stopping the machine when a signal is received from the processing unit (2) in the shortest possible time. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Safety system for the protection of a construction saw operator

TECHNICAL SECTOR

The present invention relates to a safety system, applicable to construction saws, based on a machine vision system with real-time image capture. The system, pre-trained using artificial intelligence, recognizes the operator's upper limbs and detects the risk of an accident with the cutting blade, stopping the machine in such a case.

The construction saw or wood splitter is considered one of the most dangerous light construction machines, with the highest accident rate. This is demonstrated by the fact that this type of machine is included in Annex IV of Directive 2006/42/EC of the European Parliament and of the Council on machinery. Machines included in this annex are particularly dangerous, requiring more rigorous certification procedures and specific harmonized standards.

The European Commission has published a proposal for a new machinery regulation that will repeal Directive 2006/42/EC in the near future. This proposed regulation maintains this type of machinery as a high-risk machine, and therefore will continue to have a specific and more rigorous conformity assessment procedure.

BACKGROUND OF THE INVENTION

Construction saws are widely known and used primarily in the construction sector, generally on-site. They are machines designed to cut wood or chipboard using a steel blade with hard metal teeth (usually widia, i.e., tungsten carbide).

The construction saw consists of a fixed work table with a slot that houses the cutting blade. The cutting blade is mounted on a horizontal shaft below the table, driven by an electric motor, allowing it to rotate at high speed. The material to be cut is fed manually by the operator, who is involved in sliding and guiding the material for cutting. The cutting height remains constant. The machine has a cutting ruler to assist in guiding the material to be cut, with two positions at different heights. To start the machine, actuate the switch located on the front, which starts the electric motor and begins the blade to rotate. To stop the machine, simply actuate the stop control.

The construction saw features several safety guards: a fixed guard on the lower part of the table, and an automatically adjustable guard on the upper part. The latter is transparent and in contact with the cutting table, only rising when the material to be cut is inserted. For added safety, the construction saw includes a pusher and a wedge-making accessory, which are mandatory when cutting small pieces, to prevent the operator's hands from getting too close to the cutting disc.

Despite the safety components the machine has, the reality is that they are often misused. It is common to remove the upper blade guard and fail to use the machine's built-in safety tools for small parts. This, combined with the machine's inherent danger and operator carelessness, leads to a large number of accidents with potentially very serious consequences, primarily due to cuts and amputations caused by the cutting blade.

There are several safety systems for similar machines. Some of them are described below:

Document US 2002/0170399 A1 describes a safety system that, by applying a small voltage to the cutting disc and measuring electrical conductivity, is capable of detecting contact between the skin and the cutting disc of a circular saw. As soon as it detects skin, the cutting disc is stopped by releasing a pre-tensioned cartridge, pressing on a plastic element that attaches to the cutting disc.

Document US 2009/0301275 A1 describes a safety system based on the detection of the operator's hands in the vicinity of a cutting machine tool, through electromagnetic emission and measurement of its reflection.

Document DE 20 2010 004 458 U1 describes a safety system in which several sensors detect body parts in the material feed area of a cutting machine tool. To prevent danger, the actions described include guarding the circular saw blade or lowering it below the table.

Document US 2011/0226105 A1 describes various safety systems based on detecting capacitance, electrical conductivity, radio frequency, electromagnetic waves, acoustic waves, proximity, airflow, vibration, or image capture for cutting machine tools. Actions to respond to dangerous situations include stopping the saw blade, lowering the saw blade, forming a protective screen around the saw blade (airbag), acoustic signals, and optical signals.

Document WO 2013/046522 A1 describes a safety system based on measuring the reflection of electromagnetic waves emitted by an object by three sensors located at different points around the cutting machine tool. It only detects objects that reflect electromagnetic waves, so the machine operator must wear an accessory that allows for their detection.

Document US 2013/0187026 A1 describes a safety system based on the detection of an element (such as a glove) placed on the hands of a cutting machine tool operator by means of electromagnetic or radio frequency detection.

Document US 2014/0090948 A1 describes a safety system based on detecting the proximity of human skin to a cutting machine tool using temperature and distance data collected by an infrared sensor and a presence sensor, respectively.

Document WO 2014/164964 A1 describes a system that detects the type of material being cut and its position, reducing the motor speed at the end of the cut to reduce the risk of injury to the operator of a saw.

Document US 2014/0331833 A1 describes a safety system that detects human skin contact or proximity to a saw blade using capacitive measurement. The protective measure consists of stopping the saw.

Document WO 2015/091245 A1 describes a safety system that detects the proximity between a human and a cutting tool by means of two light emitters and capturing their reflection using two photodetectors. It describes the stopping or lowering of the saw blade as a safety measure when a dangerous situation arises.

Document WO 2016/145157 A1 describes a saw safety system that detects an electrically conductive object (such as the operator's hands) by changing its capacitance, while simultaneously applying an excitation voltage. The motor stops when it approaches, and upon contact, a pyrotechnic braking device is activated, blocking the cutting disc.

Document US 2016/0279754 A9 describes the incorporation of some equipment such as motion sensors or to detect dangerous situations in power tools such as saws and other woodworking machinery.

Document WO 2017/059473 A1 describes a method for detecting human tissue in the vicinity of a tool by measuring the periodic change in capacitance.

Document AT17451 U1 describes a safety system for panel saws and/or edge banders based on three-dimensional image capture and/or infrared radiation.

Document WO2023/166207 A1 describes a safety system for a machine tool consisting of a device that is attached to the user's head and captures images of his or her field of vision.

Document US 2024/0300041 A1 describes a safety system for band saws, based on a combined artificial vision system with a camera located on the top of the saw and magnetic artificial vision with an inductive or metal sensor installed on the table, so that it is activated when it detects the color and metallic material of the gloves used by the operator.

In some of the safety systems described above, contact with the cutting blade is required. Although the detection of the operator's limbs and the safety action are very rapid, injuries can occur, and can be very serious if the speed at which the skin contacts the cutting blade is high. This also leads to user disacceptance of the safety system, mainly due to a lack of sense of security.

Some of the aforementioned safety systems only work with insulating materials, differentiating human tissue by its electrical conductivity or capacitance change. Although the construction saw is designed to cut wood (insulating material), if the wood has a certain moisture content, it will behave similarly to human tissue, making it impossible to differentiate it. This leads to false detections and machine shutdowns.

Some of the safety systems mentioned above have the disadvantage that the machine operator must wear a protective device, such as gloves, to operate them. Other safety systems mentioned above have elements that hinder normal work processes. Other safety systems mentioned above have an associated cost when activated (requiring the cutting disc, a cartridge, or similar). These drawbacks lead to a lack of user acceptance of the safety system.

Some machine vision-based safety systems have been mentioned previously. These systems use multiple cameras to perform detection, and some are even supported by another sensor. This increases the cost of the machine vision system due to the use of multiple cameras and, consequently, requires a more powerful processing unit capable of handling images from several cameras simultaneously. This makes it difficult to incorporate them into inexpensive machines such as construction saws, as the price difference for the machine with the safety system can be up to three times higher than without it, which would hinder market penetration. Furthermore, in these safety systems, the connection between the camera and the processing unit is made through a support or side arm that either limits the cut on one side when cutting large wood panels or protrudes considerably beyond the cutting table. This can be a drawback for construction saws, as they are small, manageable, and robust machines, and, due to their use outdoors and in harsh environments, they should not have any protruding elements that could be susceptible to impacts, snagging, imbalance, etc.

For these reasons, most previous safety systems have not had much market success. Therefore, the need for a safety system that reduces risk in these types of highly dangerous machines is clear. It must meet the following conditions: high levels of safety and reliability, compliance with current regulations, user acceptance, reasonable acquisition cost, zero or very low associated activation costs, and ergonomics (that does not hinder or impede the work process).

EXPLANATION OF THE INVENTION

The present invention consists of a safety system that, in the event of a dangerous situation, rapidly stops a construction saw or similar machine tool in which the workpiece to be machined is fed manually. A dangerous situation is understood to be one in which the operator of said machine approaches one or more of their upper limbs to the cutting tool to a distance below a predefined threshold.

This safety system is based on machine vision, in which a camera located at a certain distance from the cutting tool, preferably in the upper area, captures images in real time. These images are collected by a processing unit, and a pre-trained artificial intelligence algorithm detects the operator's upper limbs. If these limbs enter a danger zone delimited around the blade, the processing unit triggers an order to stop the machine. A machine stop device must stop the cutting tool in the shortest possible time, avoiding injuries to the machine operator.

The safety system described anticipates any dangerous situation, as it prevents the user from approaching the cutting tool and is therefore activated before skin contact with the cutting tool.

Thanks to the machine vision technology used, the machine operator's upper limbs can be identified regardless of the type of material being cut (insulating or conductive), as well as their morphology. Furthermore, the user does not need to wear any equipment for the safety system to work properly. The system is capable of detecting the operator's upper limbs regardless of their skin color, whether they are wearing gloves, the position in which they are positioned, and even if part of them are hidden from the camera's view by the material being cut or some element of the machine, such as the cutting tool guard.

The sizing of the machine vision system requires only one properly positioned camera to capture the entire scene around the cutting tool. With this configuration, and at least for a construction saw, the system is capable of detecting any dangerous situation despite the various elements that could hinder the performance of the machine vision system: dust from the material being cut, indoor and outdoor use, variability of light and shadows, among others. The use of a single camera simplifies the machine vision system, and it also requires no additional sensors. The processing unit is sized for this use, so the power required for image processing from a single camera is significantly lower than if more than one camera or other additional sensor were used. This, coupled with advances in machine vision systems and dedicated use of artificial intelligence in recent years, means that the cost of the safety system is moderate, allowing it to be incorporated into inexpensive machines such as construction saws and be competitive in the market.

The connection between the camera and the processing unit is made in a way that does not affect the ergonomics of the machine, specifically, that it does not limit the size of the material to be cut. For one embodiment of the invention in a construction saw, the connection of both elements is proposed through the machine's riving knife. The riving knife is a mandatory element in construction saws, serving to separate the material as it is being cut, preventing it from jamming or becoming embedded. The width of the riving knife is limited by regulations and is very similar to the width of the cutting disc, which makes it difficult to include wiring through it. To solve this problem, flat cable is used and a riving knife is designed consisting of two pieces that are riveted together. One of them has a double channel: one deeper so that the flat cable passes between both pieces and another so that when both pieces are riveted together, they are flush and the material does not experience friction when being cut and separated. This technical solution allows for proper integration of the safety system into the machine, with no elements that could hinder the normal work process.

Regarding the machine stop device, the preferred embodiment of the invention proposes the engine brake, although it could be another device. In another embodiment of the invention, it is proposed to hide the cutting disc beneath the table (and therefore remove it from the danger zone for the machine operator). Since the safety system is activated without contact and at a certain distance from the cutting tool, the proposed machine stop devices are sufficient to prevent operator injury. Therefore, the safety system has no associated cost upon activation and can be reactivated quickly after activation.

As indicated, the proposed safety system has significant advantages over current safety systems used for similar machines, in addition to achieving the proposed objectives: high level of safety and reliability, compliance with current regulations, user acceptance, reasonable acquisition cost, zero associated activation cost, and ergonomics of use.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description being made and in order to help better understand the characteristics of the invention, a set of drawings is attached as an integral part of said description, in which the following has been represented for illustrative and non-limiting purposes:

Figure 1.- Shows a schematic representation in top perspective view of the proposed safety system integrated into a construction saw.

Figure 2.- Shows a schematic representation in bottom perspective view of the proposed safety system integrated into a construction saw.

Figure 3.- Shows a detailed perspective view schematic representation of the connection between the camera and the processing unit of the proposed security system integrated into a construction saw.

Figure 4.- Shows a schematic representation in exploded view of the constructive form of the dividing blade, to allow the guidance of the cable that connects the camera and the processing unit of the proposed security system integrated into a construction saw.

Figure 5.- Shows a detailed perspective view of the virtual dangerous zone delimited around the cutting disc of the proposed safety system integrated into a construction saw.

PREFERRED EMBODIMENT OF THE INVENTION

The present invention and certain features, details and advantages thereof are explained in greater detail below, with reference to the embodiment of said invention on a construction saw.

Figures 1 and 2 show a schematic representation in top and bottom perspective views, respectively, of the proposed safety system integrated into a construction saw. The three main components of the safety system based on artificial vision can be seen, which are: camera (1), responsible for capturing images in real time, processing unit (2), responsible for processing the images in real time and determining whether a dangerous situation exists, and machine stop device (3), which in this embodiment is a motor brake, responsible for stopping the cutting disc when said dangerous situation occurs. The camera (1) is a high-resolution camera, with a high frame rate and fixed focus. The processing unit (2) must have sufficient power to be able to analyze the camera images in real time, execute the hand recognition model (previously trained) and act on the machine stop device (3) in the minimum possible time.

The camera (1) is fixed to a tubular support, which in turn is fixed to the machine's dividing blade (4). The camera is positioned, with the lens perpendicular to the machine table (6), at a vertical distance of between 200 and 600 mm from it. As for the horizontal position, the position of the camera lens (1) must coincide with the position of the cutting disc (5) and slightly offset from the machine's feed position. This area is of greatest interest, since it is where the machine operator usually makes the most dangerous approaches with his limbs to the cutting disc (5).

Other typical elements of construction saws are mentioned for illustrative purposes: manual machine start/stop control (7), cutting guide rule (8), upper guard of the cutting disc (9), lower guard of the cutting disc (10), suction intake of the upper guard of the cutting disc (11), suction intake of the lower guard of the cutting disc (12), pusher device (13) and device for cutting wedges or angled pieces (14).

The connection between the camera (1) and the processing unit (2) is made through the machine's splitting blade (4). This is shown in Figures 3 and 4. The splitting blade is mandatory in construction saws, it allows the material to be separated as it is cut, preventing it from jamming or embedding. Its thickness is limited by regulations and is similar to the thickness of the cutting disc, being around 3 mm, which makes it difficult to incorporate the connection wiring in a protected manner. For this reason, the splitting blade (4) is made in two pieces: base of the splitting blade (4a) and the splitting blade cover (4b). A double channel is machined into the base of the splitting blade (4a): a central channel with greater depth, prepared to house a flat cable, which will connect the camera (1) and the splitting blade (4), and another channel, in which the splitting blade cover (4b) will be housed. By means of several rivets (4c), the base (4a) and cover (4b) of the dividing blade are joined, leaving both elements flush in the area that divides the cut material and, therefore, avoiding friction or damage to the connection cable.

The processing unit (2) processes the images it receives from the camera (1) and determines whether there is a dangerous situation for the machine operator, in which case it acts on the engine brake (3). To do this, it uses an artificial vision system with a hand recognition model trained using artificial intelligence. This model is fed back with images of very diverse situations, especially where recognition is more difficult: different hand positions, hands of different sizes or skin color, use of gloves, shadows, dusty environment, hand on material to be cut in different positions, etc. This feedback is what provides robustness and efficiency to the model and, therefore, to the safety system. The camera (1) has a field of vision that covers the entire machine table (6), so once hand recognition is correct, it is necessary to determine when a dangerous situation occurs. To do this, a dangerous zone is virtually delimited around the cutting disc (16) by software, as shown in figure 5. This dangerous zone (16) comprises a minimum distance of between 30 and 80 mm with the cutting disc (5) for each of its limits.

The machine works normally, cutting the material and at the moment that part of a hand enters the dangerous zone (16), the processing unit (2) sends an order to the motor brake (3) to stop the motor and consequently the cutting disc, producing a complete stop in a few tenths of a second and avoiding injuries to the machine operator.

The preferred embodiment corresponds to the particularization of the invention in a construction saw. However, it should be noted that the detailed description of the embodiment is not limiting of the invention, and that there may be multiple variants, substitutions, additions, or construction details that will be evident to experts in the field after interpreting this description, drawings, and claims.

Claims (5)

1. Safety system using artificial vision for the protection of the operator of a construction saw or similar machine tool in which the workpiece to be machined is fed manually by the machine operator, comprising the following elements: - A high-resolution, high-frame-rate, fixed-focus camera (1), connected to the processing unit and responsible for taking images in real time. - A processing unit (2) which analyses the images received by the camera (1) and determines, using its artificial intelligence-trained model, whether a limb of the machine operator is in an area defined as dangerous (16). If a dangerous situation exists and consequently occurs, a signal is instantly sent to the machine stop device (3). The processing unit (2) must have sufficient power to analyse the images received from the camera (1) in real time, execute the recognition model and act on the machine stop device (3), all instantly. - A machine stop device (3), responsible for stopping the machine when a signal is received from the processing unit (2) in the shortest possible time. 2. Security system according to claim 1, wherein the camera (1) is positioned with the lens perpendicular to the machine table (6) and at a vertical distance of between 200 and 600 mm therefrom. Horizontally, the camera lens (1) is positioned to coincide with the position of the cutting disc and slightly offset to the feed position of the machine. 3. Security system according to claim 1, wherein the connection between the camera (1) and the processing unit (2) is made via the machine's dividing blade (4). Said dividing blade has a channel through which the connection cable passes. 4. Safety system according to claim 1, wherein the machine stopping device (3) consists of a motor brake, capable of stopping the cutting disc (5) in tenths of a second. 5. Safety system according to claim 1, wherein the processing unit (2) determines whether a dangerous condition exists and sends a signal to the machine stop device (3) by delimiting a virtual dangerous zone (16) around the cutting disc (5). This dangerous zone (16) comprises a minimum distance of between 30 and 80 mm with the cutting disc (5) for each of its limits.