Technical field

The present invention relates to an apparatus for assembling or manufacturing of products. Description of the prior art

Many products are manufactured or assembled using a combination of manual operations performed by humans, operations performed entirely by automatic machines, and operations performed by a combination of humans and automatic machines. Examples on such manufacturing include the manufacturing of automotive transmissions and engines, vehicle body assembly, assembly of automobile seats, assembly of steering, and assembly of wheels.

A complete manufacturing or assembly system may consist of a series of stations where operations are performed by humans and/or machines. Such a system typically consists of a conveyor where the parts of the product to be manufactured or assembled are placed, and these parts are then transported from one station to another.

The conveyor in a manufacturing system may be of the type "stop & go" in which the conveyor is stopped after having moved all products on the conveyor to the next station. The conveyor is not started until all human operators have pushed a button which signals that they are finished with their work. If one human operator is slow he will delay the entire manufacturing process. Therefore, manufacturers often prefer a conveyor that continuously moves parts and/or products for better control of production throughput. In this case, the manufacturing stations need to adapt to the continuous flow of parts and products.

Humans have the ability to move along with the moving parts/products and perform manufacturing or assembly operations on the moving parts/products. However, some automatic stations, due to precision requirements, need to stop the part/product in order to be able to perform operations on the part/product.

Today, these automatic stations are usually designed off-line to the main continuous conveyor so that the operation is performed independently of the main flow of parts and products. Alternatively, the station itself needs to be moving along with the product at the same relative speed. Current technology is complex, and prohibits these stations from being stationary and online, and to perform operations on the main conveyor that is continuously moving parts. Description of the invention

An object of the invention is to provide a possibility to perform automatic manufacturing or assembly operations with the station being stationary, without the station being offline to the main conveyor that is continuously moving products. This object is achieved with a method and an apparatus according to the independent claims.

Further advantages are achieved with the features of the dependent claims.

A basic idea of the present invention is to provide an apparatus having a conveyor for continuous movement of products, with at least one variable speed mechanism which may move a product to an automatic station in which automatic operations are performed by a machine, wherein the variable speed mechanism is arranged to move the product essentially along the line of movement of the conveyor. An apparatus according to the invention for performing consecutive operations on products comprises a conveyor for transportation of the products along a line of movement and a series of stations positioned along the conveyor. At least one of the stations is an automatic station comprising at least one machine which is arranged to perform automatic operations on the products. The apparatus is characterized in that the apparatus comprises at least one variable speed mechanism, which is arranged to move a product from the conveyor to an automatic station at which automatic operations are performed by said at least one machine and to return the product to the conveyor after the performance of the operations at the automatic station, wherein the variable speed mechanism is arranged to move the product at a lower speed than the conveyor during performance of the operations at the automatic station.

With an apparatus according to the invention operations may be performed at an automatic station on a product that is standing still or moving very slowly without the product having to be off-line. Thus, a conveyor having a constant speed may be combined with automatic stations that are standing still.

The variable speed mechanism may have one of many different forms. A man skilled in the art would easily provide the variable speed mechanism when having knowledge of the solution according to the present invention.

The variable speed mechanism may be arranged to hold the product still during performance of the operations at the automatic station. It is preferable to let the product be still as this facilitates the performance of the automatic operations by the machines.

The variable speed mechanism is arranged to move the product to the automatic station at a higher speed than the speed of the conveyor. This is preferable in that the distance to the surrounding stations may be kept reasonably large while also allowing the product to stand still during performance of the automatic operations. Thus, the product is moved faster than the speed of the conveyor to an automatic station, where it is stopped. Alternatively, it would be possible to have the variable speed mechanism arranged to just stop the product and to let it start again when the operations have been performed. This would, however, not provide sufficient space for the machines to perform their automatic operations.

The apparatus may be arranged to transfer product specific information to the automatic station in connection with the arrival of a product at the automatic station. This makes it possible to manufacture or assemble slightly different products in the stations. An example on a product where the individual products are to be slightly different from each other are cars, which may be ordered with different options.

The automatic station may comprise a number of machines, wherein the machines are arranged to be enabled in dependence of the product specific information that is transferred to the automatic station. This makes it possible to enable different machines and to enable the machines in different ways in dependence of the product specific information. Thus, different versions of the product may be manufactured in the same apparatus.

The variable speed mechanism may be arranged to move the product essentially in line with the line of movement of the conveyor. This is advantageous in that the variable speed mechanism only has to move the products along a line.

The variable speed mechanism may be arranged to move the next product into the automatic station at the same time as it moves the product, on which operations have been performed, out from the automatic station. With such a variable speed mechanism the operation of the variable speed mechanism is made efficient.

The variable speed mechanism may be arranged to move the product from the conveyor to the automatic station at an accelerating speed followed by a decelerating speed. It is not possible to increase the speed at an infinite rate. Thus, the speed has to be accelerating for a certain time period.

The accelerating speed may be followed by an intermediate constant speed, which in turn is followed by the decelerating speed. Depending on the rate of acceleration that is possible to use a constant speed may be used during a time period.

According to a second aspect of the present invention a method for performing operations on a product is provided. The method comprises the steps of arranging the product on a conveyor, and transporting the product on the conveyor along a line of movement to a series of stations positioned along the conveyor. At least one of the stations is an automatic station in which automatic operations are performed on the product by at least one machine. The method is characterized in that it comprises the steps of moving the product from the conveyor to an automatic station, performing automatic operations at the automatic station while the product is moving at a lower speed than the conveyor, and returning the product to the conveyor from the station.

With a method according to the invention operations may be performed at an automatic station on a product that is standing still or moving very slowly without the product having to be off-line. Thus, a conveyor having a constant speed may be combined with automatic stations that are standing still.

The product may be standing still during performance of the operations at the automatic station. It is preferable to let the product be still as this facilitates the performance of the automatic operations by the machines. The products may be arranged on supporting means, which in turn is arranged on the conveyor. By having the products arranged on supporting means it is easier to position the products stably on the conveyor. The supporting means may be in the form of pedestals on which the products are mounted during the travel through the apparatus.

The product specific information may be transferred to the automatic station before the performance of the operations at the automatic station. This is preferable in order to save time as machines at the automatic station then may be prepared to the product specific information in advance.

The operations may be performed at the automatic station in dependence of the product specific information. This makes it possible to manufacture or assemble slightly different products in the stations. Examples on products which are to be slightly different are cars, which may be ordered with different options.

The product may be moved from the automatic station at an accelerating speed followed by a decelerating speed. It is not possible to increase the speed at an infinite rate. Thus, the speed has to be accelerating for a certain time period. Short description of the drawings

Fig 1 shows schematically an apparatus for performing consecutive operations on products during operation of the apparatus.

Fig 2 shows schematically a part of the apparatus in Fig 1 during operation at a first point in time. Fig 3 shows schematically the part of the apparatus in Fig 2 during operation at a second point in time.

Fig 4 shows schematically a part of the apparatus in Fig 2 during operation at a third point in time.

Fig 5 shows schematically a part of the apparatus in Fig 2 during operation at a fourth point in time.

Fig 6 shows schematically in a side view a part of the conveyor and the variable speed mechanism. Description of preferred embodiments

In the following description of preferred embodiments of the invention similar features in the different figures will be denoted with the same reference numeral. Fig 1 shows schematically an apparatus 1 for performing consecutive operations on products 2 during operation of the apparatus 1. The consecutive operations that are performed may be assembly operations or manufacturing operations. The apparatus 1 comprises a conveyor 3 for transportation of the products 2 along a line of movement 4 and a series of stations positioned along the conveyor 3. The stations are delimited by borders 9 shown as dotted lines in the figure. A number of the stations are manual stations 5 in which a human worker performs operations on the product 2 that moves along the conveyor 3 in the station. The human worker starts working on the product as it enters the station and moves with the product as in moves along the station on the conveyor. At least one of the stations is an automatic station 6 in which automatic operations are arranged to be performed by machines 7 on the products 2. The machines 7 are robots in the embodiment shown in Fig 1. The apparatus 1 comprises at least one variable speed mechanism 8, which is arranged to move a product 2 from the conveyor 3 to an automatic station 6 at which automatic operations are performed by the machine 7 and to return the product 2 to the conveyor 3 after the performance of the operations at the automatic station 6. The variable speed mechanism 8 is arranged to move the product 2 at a lower speed than the conveyor 3 during performance of the operations at the automatic station 6. Preferably, the variable speed mechanism 8 is arranged to hold the product still during performance of the operations by the machine 7. The variable speed mechanism 8 is arranged to move the products 2 rapidly from the conveyor 3 to a position 10 for performing the operations by the machine 7. The variable speed mechanism 8 is arranged to move the products 2 along the same line of movement as the conveyor 3. The products 2 are initially moved at an increasing speed. Before coming to a halt at the position 10 for performing the operations the speed of the product 7 is decreased. Between the time period with an increasing speed and the time period with a decreasing speed, the speed of the product 2 may be constant or varying. After the operations at the automatic station 6 have been performed the product 2 is moved be the variable speed mechanism 8 along the line of movement 4 to the conveyor 3. The products 2 are then initially moved at an increasing speed. Before entering the conveyor 3 the speed of the product 7 is decreased to the speed of the conveyor 3. Between the time period with an increasing speed and the time period with a decreasing speed, the speed of the product 2 may be constant or varying.

The conveyor 3 may run continuously past the variable speed mechanism 8. Alternatively the conveyor may be divided into a number of conveyor segments between the variable speed mechanisms 8. However, in case the conveyor 3 is divided into different conveyor segments they are preferably driven by a common drive mechanism (not shown). Most importantly the conveyor segments move at the same speed. Preferably, the speed of the conveyor 3 is constant over time. Fig 2 shows schematically a part of the apparatus 1 in Fig 1 during operation at a first point in time T ₁ . A first human operator 11 is stationed in a first manual station 12. The first operator 11 has just finished the work on the product A which is half its way into the next station. The machine 7 in the form of a robot has finished all operations on the product B, which is situated in the middle of the automatic station 6 on the variable speed mechanism 8. A second human operator 13 is stationed in a second manual station 14. The second operator 13 has just finished the work on the product C which is half its way into the variable speed mechanism 8. A fourth product D is entering the second manual station 14. Each one of the products A-D is arranged on a supporting means 15 such as a pedestal. This makes it easier to position the products on the conveyor 3. The first product A and the fourth product D are driven by the conveyor while the second product B and the third product C are driven by the variable speed mechanism 8. The variable speed mechanism 8 has been standing still while the machine 7 has been performing its operations and is just about to start moving again. The machine 7 is preparing to start mounting pistons 16 on the product C, which is an engine, by picking a piston 17 from the stand 28.

Fig 3 shows schematically the part of the apparatus in Fig 2 during operation at a second point in time T ₂ . The variable speed mechanism 8 has just moved the second product forward along the line of movement 4 to the conveyor 3 and has at the same time moved the third product into the automatic station 6. The machine 7 has started to mount a piston 17 on the product C. At the same time as the second product B and the third product C are moved by the variable speed mechanism the fourth product D has moved a small distance and has fully entered the second manual station 14. The first human operator 11 has started to work on the second product B and the second human operator 13 has started to work on the fourth product D. At each one of the stations there is arranged an information device 18, which may be a computer. Information on the products is transferred between the information devices 18. The transfer of the information is synchronised with the movement of the products. When the fourth product D enters the second manual station 14, product specific information is transferred to the information device 18 which is arranged in the second manual station. The information may differ between different products A-D. The product specific information comprises information on which operations that are to be performed by the operator and may be displayed on a screen (not shown) on the information device 18, 22. The entrance of a product into the different stations is detected by sensors 19 which are positioned at the borders 9 and connected to the information devices 18. When the third product C enters the automatic station 6 the product specific information is transferred to the information device 20 which is arranged in the automatic station 6 and which is connected to the machine 7. The machine 7 is enabled in dependence of the product specific information that has been transferred to the information device 20 which is arranged in the automatic station 6. The information device 20 may also function as a controller for the automatic station. The product specific information may comprise a product unique number (PUN), build status and similar.

Fig 4 shows schematically a part of the apparatus in Fig 2 during operation at a third point in time T ₃ . The machine 7 in the automatic station 6 has mounted one piston 17 and is about to mount the second piston 17. Compared to the situation shown in Fig 3 the second product B and the fourth product D have both moved a small distance along the conveyor 3 and the human operators 12, 13, have performed operations in accordance with the information provided by the information devices 18, 22. Fig 5 shows schematically a part of the apparatus in Fig 2 during operation at a fourth point in time T ₄ . The machine 7 in the automatic station 6 has mounted three pistons 17 and is about to mount the fourth piston 17. Compared to the situation shown in Fig 3 the second product B and the fourth product D have both moved along the conveyor 3 and the human operators 12, 13, have finished their operations in accordance with the information provided by the information devices 18, 22. When the machine 7 has finished its operations it shall send a signal to the information device/controller 20. If the machine 7 is not finished with its operations on the third product C when the fourth product D is about to enter the automatic station 6 the information device/controller 20 will send a signal to the main controller 23, which will stop the conveyor 3. If the conveyor 3 has been stopped, it will be restarted by the main controller 23 upon receiving a start signal from the information device/controller 20. The apparatus 1 is then back in a situation similar to the one showed in Fig 2.

Fig 6 shows schematically in a side view a part of the conveyor 3 and the variable speed mechanism 8. The conveyor 3 is guided below the variable speed mechanism 8 by rolls 24. In Fig 6 is also shown push blocks 25 that are arranged in the middle of the conveyor 3. The push blocks 25 are arranged to push on the supporting means 15 on which the products A-D are arranged. The rolls 24 may have a smaller diameter at the middle of the conveyor to allow the push blocks 25 to pass the rolls 24.