DOUBLE SPINDLE CIRCULAR SAW FOR SAWING WOOD

Description

Technical area

[0001] The invention relates to a double-spindle circular saw according to the preamble of claim 1. State of the art

[0002] The use of double-spindle circular saws has become established in recent decades in the field of sawing technology for processing round and squared timber. Devices of this type are known, for example, from DE 40 38 129 A and EP 0 785 051 A. The key advantages of this technology are a cutting surface with the best surface properties, precise cutting edge retention, and very high cutting performance. The circular saw itself can be designed as a group saw, i.e., it can perform multiple cuts simultaneously with several saw blades arranged on a common tool, allowing particularly high volume outputs to be achieved with relatively simple machines.

[0003] Due to the circular saw blades and their maximum practical diameter, double-spindle circular saws have a limited cutting height for technical reasons. Therefore, the cutting process is also carried out from two opposite sides, with two saw groups, with the saw blades always working in pairs in a common cutting plane. The material to be cut is pushed through the double-spindle circular saw between the saw spindle axes using a suitable conveyor drive.

[0004] In addition, the two saw groups are offset in the cutting direction, ensuring a vertical overlap of several millimeters between the centrifugal circles of the circular saw blades operating in the same cutting plane, ensuring clean cutting of the lumber. This overlap, free of lateral offset, is a prerequisite for a flat surface of the sawn material.

[0005] To ensure this, the radial distance between the saw spindles of the saw groups must be adjustable, depending on the circular saw blade diameter. They must also be height-adjustable for horizontal spindles and laterally adjustable for vertical spindles, so that the different total cutting heights can be equally divided between both saw groups. To avoid lateral offset, the position of the saw spindles is adjustable in the direction of the saw spindle axis.

[0006] For small saw units not used in double-spindle circular saws, it is common practice to use smaller saw spindle motors with lower motor power and a short, overhanging saw shaft stub. However, these are not suitable for use in double-spindle circular saws, as the motors' power-related dimensions prohibit their use. It is not possible to scale up a smaller unit to the size needed for use in a double-spindle circular saw. Therefore, the conventional sawing tools are mounted at both ends in a machine frame, and the saw spindles are driven by belt drives, which in turn places a very high alternating load on the saw spindle.

[0007] For illustrative purposes, the technical specifications of a saw group are shown. A motor power of approximately 600 kW (at 3000 rpm) is required, with the motor speed varying from 0 to 4000 rpm. The outer diameter of a standard motor for this purpose would be approximately 900 mm, requiring circular saw blades with at least this diameter.

[0008] A known sawing machine (DE 19955590 A1) has a plurality of saw-axis arrangements, namely four per machine unit, that can be independently adjusted transversely to the feed direction of the sawn material. Each of the four saw axes carries at least one saw blade that cuts into the sawn material. The wood is thus cut between four saw axes and not between two, as in a double-spindle circular saw according to the invention. Furthermore, the sawing machine comprises several machine units.

[0009] The drive power and speed are derived from experience with conventional high-performance circular saws which use a separate saw spindle and require power to be transmitted via belts. The belt tension required for a belt drive of this size far exceeds the bearing load caused by regular cutting forces. Such forces therefore require larger bearings which, in turn, are not suitable for the required speeds. To circumvent this problem, belt drives have been proposed which consist of two belts offset by 180 degrees from each other and pulling in opposite directions. The fact that the saw spindles have to be adjusted relative to each other results in a very complex construction weighing around 5 tons, with a cutting accuracy of less than 0.1 mm.

[0010] WO 00 / 67967 A1 discloses a double-spindle circular saw according to the preamble of claim 1. Description of the invention

[0011] The invention is therefore based on the object of creating a double-spindle circular saw of the type described above, which allows a clean cut within narrow tolerances and at the same time is compact and enables a quick and easy change of saw tools.

[0012] The invention solves the stated problem by a double-spindle circular saw with the combination of features of claim 1. Advantageous further developments of the invention can be found in the dependent claims.

[0013] Because the motor is mounted directly on the saw spindle, eliminating the need for external drives that place excessive strain on the saw spindle, there is no excessive bending stress on the shaft and no resulting deflection of the sawing tool attached to the saw spindle. This allows for clean cutting within tight tolerances and the floating mounting of the sawing tool. This floating mounting of the sawing tool, in turn, enables quick and easy sawing tool changes. The drive, particularly an electric motor or similar, with the heavy saw spindle and its high moment of inertia, is very advantageous for smoothing out the shock loads that occur during sawing and for preventing the continuation of these shock loads in the electrical system and subsequent damage.

[0014] The result of this very advantageous arrangement is that the drive armature sits directly on the saw spindle between the fixed bearing and the floating bearing. The fixed bearing is arranged specifically between the armature and the saw tool in order to keep dimensional tolerances in the event of temperature changes in the saw spindle and the associated change in length to a very small extent. To ensure that the outer diameter of the drive, especially of the electric motor, is kept small enough – it must be smaller than the circular saw blade diameter to enable appropriate adjustment of the two axes with the correct distance – the armature and thus the stator length must correspond to this. The circular saw blade diameter should be kept as small as possible – since an outer diameter that is too large would have a negative impact on the rigidity of the circular saw blades and thus on the cutting result.

[0015] Compared to the state of the art, which features additional power transmission elements in addition to the drive motor and thus additional sources of loss, the saw assemblies according to the invention offer significantly higher efficiency. An improvement of approximately four percent can be expected.

[0016] With a double-spindle circular saw according to the invention, the wood can be cut on both sides of its apex plane per spindle with saw blades firmly clamped on a saw bushing between saw blade gauges.

[0017] To simplify the changing of the sawing tool, in particular the sawing groups, as is necessary during operation for each product (dimension) change and for a cutting edge change, the sawing tool preferably comprises at least one saw blade, in particular a circular saw blade group, which is exchangeably mounted on a tool clamp, a type of bushing.

[0018] The tool clamp can be attached to the saw spindle via a keyway. For this purpose, the tool clamp, for example, has a coaxial, cylindrical bore and thus sits on a corresponding spindle stub assigned to the saw spindle. Torsional rigidity is ensured by a keyway.

[0019] However, it is particularly advantageous if the tool clamp is detachably attached to the saw spindle via a quick-change cone, which has a corresponding counterpart in the form of a conical spindle stub, and is preferably secured in the assembled position with a screw connection coaxial with the saw spindle axis. The use of the saw bushing with the quick-change cone and screw locking device is possible due to the floating mounting of the saw tool, allowing for particularly rapid saw tool changes. Furthermore, the tubular tool clamp offers the possibility of significantly improving the operating conditions of the circular saw blades.

[0020] If a head for operating the screw connection is mounted in the tool clamp so that it can rotate freely but is axially secured, then the tool clamp can not only be advantageously secured on the saw spindle, but can also be removed from the saw spindle, since the screw connection also acts as a removal tool.

[0021] The quick-change cone shown is not limited to use with the present invention. It can also be used independently on known double-spindle circular saws.

[0022] In order to be able to transmit particularly high power levels, a further development of the invention provides for the electric motor to be liquid-cooled to avoid thermal problems. Furthermore, the armature, the stator, the fixed bearing, and the floating bearing can be liquid-cooled, for which purpose four cooling circuits whose temperatures can be independently controlled by means of temperature control valves are preferably provided. This allows the thermal effects of the electric motor on the bearings arranged in the same housing, as well as the bearing power losses, to be absorbed by intelligent liquid cooling. The liquid cooling can also be equipped with a temperature control and, if necessary, a heater to prevent temperatures from falling below the dew point in the housing.It is advantageous to maintain the temperature of the cooling medium within a desired range, as much as possible, by heating during standstill and cooling during operation, to avoid temperature-related dimensional changes in the saw spindle. The required flow rate for each of the four cooling circuits can be individually and independently controlled using thermostatic valves, ensuring maximum temperature consistency at the optimal (and quite different) level for each of the four cooling circuits, thus ensuring operating accuracy and availability.

[0023] When the motor is in operation, a considerable amount of heat can be introduced into the housing via the electric motor, which must then be dissipated accordingly. For direct cooling of the armature, the saw spindle, and the inner rings of the bearings, it is recommended that the saw spindle be liquid-cooled via a rotary union assigned to the end of the saw spindle facing away from the saw tool. For this purpose, a sleeve connected to the rotary union is inserted into a bore that is coaxial with the saw spindle axis and extends in the axial direction, preferably over the loose bearing, armature, and fixed bearing, in such a way that a flow channel is formed between the bore wall and the sleeve. A coolant is introduced into the bore and flows through the bushing to its end area at the other end of the saw spindle, where it crosses into the flow channel between the bushing and the bore wall. From there, the coolant flows in the opposite direction and is discharged from the housing.

[0024] To cool the stator, the stator can be inserted into the housing in such a way that a flow channel for liquid cooling of the stator is formed between the stator and the housing and / or within the housing surrounding the stator. When controlling the temperature of the stator, it is important to ensure a consistent operating and idle temperature to prevent damage to the insulation of the stator winding during operation due to the constant (inherent) current fluctuations and the resulting thermal expansion and contraction caused by temperature fluctuations, thus preventing a short circuit or ground fault.

[0025] To cool the bearings, they can be installed in the housing in such a way that the floating bearing and / or locating bearing are inserted on the outer circumference into a bushing arranged in a bearing block within the housing, which is fixed against rotation. A flow channel for liquid cooling of the bearings is formed between the bushing and the bearing block. Cooling the outer bearing rings further stabilizes the system and makes it fatigue-resistant, as required for virtually clearance-free locating bearings and industrial applications.

[0026] In all cases, it is advantageous if the flow channel runs helically around the saw spindle axis. This ensures uniform cooling and thus even temperature distribution across the entire surface.

[0027] Since the permissible limit speed generally decreases with larger bearings, it is advantageous if the floating bearing and the locating bearing each comprise at least one rolling bearing connected via fluid lines to a preferably central oil-air lubrication device. This enables the required high speeds with low losses and long maintenance intervals. Oil-air lubrication, with which minimal amounts of oil are blown directly onto the rolling elements in the form of streaks, enables the high speeds for the bearing size and creates overpressure inside the bearing housing, thus preventing the ingress of dirt. In addition, fine abrasion debris from bearing operation is washed away with the used oil flowing out through the drainage holes, which is not possible with grease lubrication, for example.

[0028] The stator coils are preferably made of shaped wire, i.e., wire with a triangular, square, or polygonal cross-section, for example. This avoids point contact points across the cross-sectional circumference, thus preventing damage to the insulation even after frequent temperature-induced wire length changes. For the same reason, it is proposed that the pole ends of the stator coils exit the housing at the end and / or floating bearing sides in an axial direction, particularly parallel to the saw spindle axis. Brief description of the invention

[0029] The drawing shows an example of the subject matter of the invention. Fig. 1a double-spindle circular saw in front view, Fig. 2a saw group of the double-spindle circular saw in schematic longitudinal section, Fig. 3the enlarged and more detailed left section with the fixed bearing of the saw group from Fig. 2 and Fig. 4 the enlarged and more detailed right section with the floating bearing of the saw group from Fig. 2 Ways to implement the invention

[0030] The double-spindle circular saw 1 for sawing wood 2 comprises two saw groups 3. The saw groups 3 are offset in the cutting direction 4 of the wood 2 to be cut. Each saw group 3 has an electric motor 7 comprising an armature 5 and a stator 6 for rotary driving a saw spindle 9 mounted in a housing 8. The saw spindle 9 is rotationally fixedly connected to at least one sawing tool 11 comprising at least one replaceable circular saw blade 10. When driven, the sawing tool 11 and the saw spindle 9 thus rotate together at the same angular velocity. The center distance A of the saw spindles 9 can be adjusted using an actuator (not shown in detail).The lateral offset of the saw tools 11 relative to one another in the direction of the saw spindle axis 12 can also be adjusted with this or another adjusting drive in order to ensure that the circular saw blades 10 of the two saw tools are exactly aligned with one another and lie in one and the same cutting plane.

[0031] According to the invention, the armature 5 is non-rotatably mounted on the saw spindle 9, and the stator 6 is non-rotatably mounted in the housing 8 between a fixed bearing 13 and a floating bearing 14 of the saw spindle 9. The sawing tool 11 is cantilevered on the saw spindle 9. The saw groups 3 are arranged parallel to the saw spindle axes and with the housing 8 aligned in the same way in a machine frame or the like (not shown in detail).

[0032] The sawing tool 11 comprises at least one saw blade 10, optionally two or more saw blades 10, in particular a circular saw blade group, which is interchangeably mounted on a tool clamp 15. The tool clamp 15 is detachably attached to the saw spindle 9, which has a corresponding counterpart in the form of a conical spindle stub 17, via a quick-change cone 16 in the manner of a steep taper (for example, 7 / 24), and is secured in the assembled position by a screw connection 18 coaxial with the saw spindle axis 12. In the exemplary embodiment, the spindle stub 17 is a transition piece mounted on the end of the saw spindle, but can also be formed directly from the saw spindle. A head 19, a screw or nut head, for actuating the screw connection with a corresponding tool is freely rotatable but axially secured in the tool clamp 15.For this purpose, the head 19 is equipped with a shoulder 20 which rests on the tool clamp 15 at one end when the screw connection is tightened and is supported on an annular disk 21 when the screw connection is loosened and the tool clamp 15 is pulled off the axle stub 17.

[0033] The drive, in particular the electric motor 7, is liquid-cooled. The armature 5, the stator 6, the fixed bearing 13, a group of rolling bearings, and the floating bearing 14 are also liquid-cooled. For this purpose, four cooling circuits are provided, the temperatures of which can be independently controlled by means of temperature control valves 22. To prevent the temperature in the housing from falling below the dew point, the cooling circuits can be equipped with a temperature control system, which can optionally be assigned a heater to ensure the drive can be kept at the correct temperature even when the motor is at a standstill.

[0034] To cool the armature 5 and the inner rings of the fixed bearing 13 and loose bearing 14 via the saw spindle 9, the saw spindle 9 is liquid-cooled via a rotary feedthrough 23 assigned to the end of the saw spindle 9 facing away from the saw tool. For this purpose, a sleeve 25 connected to the rotary feedthrough 23 is inserted into a bore 24 coaxial with the saw spindle axis 12 and extending in the axial direction preferably over the loose bearing, armature, and fixed bearing in such a way that a flow channel 26 is formed between the bore wall and the sleeve 25. The stator 6 is inserted into the housing 8 in such a way that a flow channel 26 for liquid cooling the stator 6 is formed between the stator 6 and the housing 8 or in the housing 8 surrounding the stator 6. In the present exemplary embodiment, the flow channel 26 is provided in the housing 8 between a stator receptacle and a housing shell.For cooling, the floating bearings and / or fixed bearings are inserted on the outer circumference into a bushing 28 arranged in a bearing block 27 in the housing in a rotationally fixed manner. The flow channel 26 for liquid cooling of the bearings is formed between the bushing 28 and the bearing block 27. The flow channels for the bearing cooling, the armature cooling, and the shaft cooling run helically around the saw spindle axis 12.

[0035] For cooling and lubricating the floating bearing 14 and the fixed bearing 13, these are each connected to a central oil-air lubrication device 30 via at least one fluid line 29.

Claims

1. Dual-spindle circular saw (1) for sawing wood (2) comprising two saw groups (3), wherein each saw group (3) has a drive (7) having an armature (5) and a stator (6) for the rotary driving of a saw spindle (9) which is mounted in a housing (8) and which is connected in a rotationally fixed manner to a saw tool (11) comprising exchangeable circular saw blades (10), and wherein the saw tool (11) is floatingly mounted on the saw spindle (9), characterized in that the armature (5) is arranged in a rotationally fixed manner on the saw spindle (9) and the stator (6) is arranged in a rotationally fixed manner in the housing (8) between a fixed bearing (13) and a floating bearing (14) of the saw spindle (9), wherein the center distance (A) of the saw spindles (9) is adjustable by means of an actuator.

2. Dual-spindle circular saw according to claim 1, characterized in that the saw tool (11) comprises a circular saw blade group interchangeably accommodated on a tool clamp (15), wherein the tool clamp (15) is detachably fastened via a quick-change cone (16) to the saw spindle (9) having a corresponding counterpart in the form of a conical axle stub (17) and is preferably secured in the mounting position by means of a screw connection (18) coaxial with the saw spindle axis (12).

3. Dual-spindle circular saw according to claim 2, characterized in that a head (19) for actuating the screw connection (18) is mounted in the tool clamp (15) so as to be freely rotatable but axially secured.

4. Dual-spindle circular saw according to one of claims 1 to 3, characterized in that the armature (5) and / or the stator (6) of the drive (7) are liquid-cooled.

5. Dual-spindle circular saw according to one of claims 1 to 4, characterized in that the armature (5), the stator (6), the fixed bearing (13) and the floating bearing (14) are liquid-cooled, for which purpose preferably four cooling circuits which can be temperature-controlled independently of one another by means of temperature control valves (22) are provided.

6. Dual-spindle circular saw according to claim 4 or 5, characterized in that the liquid cooling system is equipped with a temperature control (T) to prevent undershooting of the dew point in the housing (8).

7. Dual-spindle circular saw according to one of the claims 1 to 6, characterized in that the saw spindle (9) is liquid-cooled via a rotary union (23) assigned to the end of the saw spindle (9) facing away from the saw tool, for which purpose a sleeve (25) connected to the rotary union (23) is inserted into a bore (24) coaxial with the saw spindle axis (12), preferably via the floating bearing (14), armature (5) and fixed bearing (13) in the axial direction, in such a way that a flow channel (26) is formed between the bore wall and sleeve (25).

8. Dual-spindle circular saw according to one of claims 1 to 7, characterized in that the stator (6) is inserted into the housing (8) in such a way that a flow channel (26) for liquid cooling of the stator (6) is formed between the stator (6) and the housing (8) and / or the housing (8) enclosing the stator (6) has a flow channel (26) for liquid cooling of the stator.

9. Dual-spindle circular saw according to claim 8, characterized in that the housing (8) is provided with a jacket tube around its outer circumference, wherein the flow channel (26) for liquid cooling of the stator is formed between the jacket tube and the stator (6), in particular between the jacket tube and the housing (8).

10. Dual-spindle circular saw according to one of claims 1 to 9, characterized in that floating bearings (14) and / or fixed bearings (13) are inserted on the outer circumference into a bushing (28) arranged in a rotationally fixed manner in the housing (8) in a bearing block (27), wherein a flow channel (26) for liquid cooling of the bearings is formed between the bushing (28) and the bearing block (27).

11. Dual-spindle circular saw according to one of claims 7 to 10, characterized in that the flow channel (26) extends helically around the saw spindle axis (12).

12. Dual-spindle circular saw according to one of claims 1 to 11, characterized in that floating bearing (14) and fixed bearing (13) each comprise at least one rolling bearing connected via fluid lines (29) to a preferably central oil-air lubrication device (30).

13. Dual-spindle circular saw according to one of claims 1 to 12, characterized in that the coils of the stator (6) are formed of shaped wire.

14. Dual-spindle circular saw according to one of the claims 1 to 13, characterized in that the pole ends of the coils of the stator (6) are guided out of the housing on the end face side and / or floating bearing side in the axial direction, in particular parallel to the saw spindle axis.