Roll grinder with precision adjustment device

Abstract

The present application belongs to the field of roll grinder, and proposes a roll grinder with precision adjustable device, which comprises a grinder, a prior measurement driving device, a main moving seat, a vice moving seat and a feeding and withdrawing screw driving mechanism, the feeding and withdrawing screw driving mechanism and the main moving seat are both provided with an on-line measurement device, the prior measurement device comprises a 90-degree switching motor, a rack and a measurement rack, the measurement rack comprises a C-shaped measurement ring opening, and the measurement ring openings of different measurement racks are different in diameter, the top surface and the bottom surface of the measurement ring opening are both provided with a group of displacement sensors, the detection end of the displacement sensor is provided with a contact assembly, and the center of the contact assembly is provided with an adjusting mechanism for adjusting the contact form with the roll. The present application can simultaneously detect multiple sites, can adjust the detection precision, is beneficial to improve the measurement precision and is beneficial to improve the processing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of roll grinding machines and relates to a roll grinding machine with an adjustable precision device. Background Technology

[0002] Roll grinding machines are heavy-duty, ultra-high precision specialized cylindrical grinding machines, specifically designed for grinding the core components of rolling mills in the metallurgical, papermaking, rubber, and film industries—the rolls. During the rolling of sheet metal, rolls experience wear, surface defects, and sheet shape deviation, necessitating regular over-grinding. The precision roll shape, micron-level dimensions, and mirror-like surface achieved by these grinding machines directly determine the flatness, thickness uniformity, and finished product yield of the strip. Besides adjusting the precision of the grinding tools, roll grinding machines also require precision adjustments to the online measurement equipment for measuring the surface quality. Simultaneously, workers conduct light inspections of the ground surface to ensure the grinding quality of the rolls.

[0003] Most grinding machines employ mechanical dial indicators or displacement sensors for precision measurement. The dial indicator is mounted on the tool holder of the grinding tool using a mounting bracket, and the tool holder is driven linearly and reciprocally by the grinding machine's horizontal drive mechanism. However, this design can lead to measurement errors in the dial indicator due to the influence of both the grinding machine and the tool holder. Some existing roll grinding machines use relatively independent designs for precision measurement. While this allows for online precision measurement, it prevents simultaneous detection at two positions with two sets of grinding tools operating at intervals, resulting in a relatively delayed precision measurement operation. Furthermore, most dial indicators and displacement sensors can only perform point contact detection, requiring point-by-point detection during secondary inspections, increasing the secondary inspection cycle. Finally, since some rolls require full-shaft grinding, the more positions where the shaft diameter changes, the more frequently a single online precision measurement device needs to be adjusted, especially when the online precision measurement device is set in pairs radially; frequent adjustments can increase measurement errors. Summary of the Invention

[0004] This invention addresses the technical problems of the prior precision measuring devices used in the aforementioned roll grinding machines by proposing a roll grinding machine with an adjustable precision device that can simultaneously detect multiple points, adjust the detection precision, improve measurement accuracy, and enhance processing efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a roll grinding machine with an adjustable precision device, comprising a grinding machine, a spindle and a tailstock, two sets of moving grinding devices for grinding rolls at intervals are arranged between the spindle and the tailstock, a prior measurement drive device independent of the grinding machine is arranged on one side of the grinding machine, the prior measurement drive device is equipped with a control box and a guardrail, the power output end of the prior measurement drive device is equipped with a main moving seat and a secondary moving seat with parallel moving trajectories, and the secondary moving seat is equipped with a forward and backward screw drive mechanism perpendicular to the moving direction. The lead screw drive mechanism and the main moving seat are both equipped with online measuring devices. The prior measuring device includes a 90-degree switching motor. The power output end of the 90-degree switching motor is equipped with a frame. The frame is equipped with two measuring frames connected to it and staggered at 90 degrees. The measuring frames include C-shaped measuring rings, and the diameter of the measuring rings of different measuring frames is different. A set of displacement sensors is provided on the top and bottom surfaces of the measuring rings. The detection end of the displacement sensor is equipped with a contact component. The center of the contact component is equipped with an adjustment mechanism for adjusting its contact form with the roll.

[0006] Preferably, the contact assembly includes a mounting base, and the center of the mounting base is provided with a contact plate that dynamically contacts the detection end of the displacement sensor. The contact plate includes a point contact surface, a first line contact surface, and a second line contact surface. The lengths of the first line contact surface and the second line contact surface are different and both are tangent to the circumference of the point contact surface.

[0007] Preferably, the contact plate has a measuring stroke circular hole and a cross stroke hole that communicates with the measuring stroke circular hole at its center. The adjustment mechanism includes a rotating flap, which includes a circular segment that mates with the measuring stroke circular hole and a straight segment that mates with the cross stroke hole. The length of the straight segment is less than the unidirectional length of the cross stroke hole. The driving end of the rotating flap is equipped with a dual servo telescopic rotary electric cylinder.

[0008] Preferably, the inner side of the mounting base is provided with a clutch groove for the rotating disc to quickly disengage from the contact plate.

[0009] Preferably, the mounting base is provided with a sealing end plate at its end, and a positioning groove is provided between the sealing end plate and the contact plate to axially move and cooperate with the sealing end plate. A spring is provided between the positioning groove and the sealing end plate, and a plurality of braking cylinders are provided at the end of the positioning groove. The braking cylinders cooperate with the positioning blind grooves provided on the contact plate.

[0010] Preferably, the end of the measuring frame is provided with a mounting groove for mounting a displacement sensor, and the outer side of the mounting groove is provided with a screw hole for mounting a locking screw and an adjusting bolt hole for mounting an adjusting bolt, the adjusting bolt connecting the measuring frame and the contact assembly.

[0011] Preferably, the measuring stroke of the main moving seat is greater than that of the auxiliary moving seat, the horizontal moving measuring rate of the main moving seat is greater than that of the auxiliary moving seat, and the main moving seat and the auxiliary moving seat share a common power source and are connected by a reduction gear.

[0012] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. The present invention provides a roll grinding machine with an adjustable precision device. By employing two sets of online measuring devices, which are driven to translate by the main moving seat and the auxiliary moving seat respectively, it can cooperate with two sets of grinding tools that operate at intervals to achieve simultaneous detection of different axial positions, which is beneficial to improving the immediacy of precision measurement operations.

[0013] 2. The present invention provides a roll grinding machine with an adjustable precision device, which can realize various forms of contact detection, such as point contact and line contact, by using contact components, which can shorten the secondary detection cycle and improve processing efficiency.

[0014] 3. The present invention provides a roll grinding machine with an adjustable precision device. By employing two sets of online measuring devices and having four different measuring rings, the adjustment frequency of the displacement sensor can be reduced, which is beneficial to ensuring measurement accuracy and processing efficiency. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a working diagram of a roll grinding machine with an adjustable precision device. Figure 2 This is a front view of a roll grinding machine with an adjustable precision device; Figure 3 This is a top view of a roll grinding machine with an adjustable precision device; Figure 4 A perspective view of the online measuring device provided in the embodiment at its initial position; Figure 5 A top view of the online measuring device provided in the embodiment at its initial position; Figure 6 A perspective view of the online measuring device provided in the embodiment; Figure 7 A top view of the online measuring device provided in the embodiment; Figure 8 for Figure 7 A cross-sectional view of the online measuring device along the GG direction; Figure 9 for Figure 7 A cross-sectional view of the online measuring device along the EE direction; Figure 10 Exploded view of the contact assembly provided in the embodiment; Figure 11 A front view of the contact plate provided in the embodiment; In the above figures: 1. Grinding machine; 11. Spindle; 12. Tailstock; 13. Moving grinding device; 2. Prior measurement drive device; 3. Control box; 4. Guardrail; 5. Main moving seat; 6. Secondary moving seat; 7. Forward and backward lead screw drive mechanism; 8. Online measurement device; 81. 90-degree switching motor; 82. Machine frame; 821. Bushing; 822. Extension plate; 823. Slot plate; 83. Measuring frame; 831. Mounting slot; 832. Screw hole; 833. Adjusting bolt hole; 834. Measuring ring; 84. Displacement Sensor; 85. Contact assembly; 851. Mounting base; 852. Contact plate; 8521. Point contact surface; 8522. First line contact surface; 8523. Second line contact surface; 8524. Measuring stroke circular hole; 8525. Cross stroke hole; 8526. Positioning blind groove; 853. Adjustment mechanism; 8531. Rotating flap; 8532. Dual servo telescopic rotary electric cylinder; 854. Clutch groove; 855. Sealing end plate; 856. Positioning circular groove; 857. Spring; 858. Braking cylinder; 9. Roller. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" appearing below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0018] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0019] Examples, such as Figures 1-11As shown, the present invention provides a roll grinding machine with an adjustable precision device, comprising a grinding machine 1, which includes a spindle 11 and a tailstock 12. Two sets of movable grinding devices 13 for intermittently grinding rolls 9 are arranged between the spindle 11 and the tailstock 12. A prior measurement drive device 2, independent of the grinding machine 1, is arranged on one side of the grinding machine 1. A control box 3 and a guardrail 4 are mounted on the prior measurement drive device 2. The two sets of movable grinding devices 13 are driven by different lead screw mechanisms and grind different shaft diameter positions of the rolls 9 separately. The control box 3 is electrically connected to a displacement sensor 84, which can display the detected real-time data on a screen. The bottom of the guardrail 4 is a manual platform where workers can perform light inspection of the grinding condition of the rolls 9. The grinding machine 1, movable grinding devices 13, control lines, and guardrail 4 are existing mature technologies and will not be described in detail here.

[0020] Based on this, the prior measurement drive device 2 provided by the present invention has a main moving seat 5 and a secondary moving seat 6 with parallel movement trajectories at its power output end. The control box 3 and the guardrail 4 are mounted on the main moving seat 5 and move with the main moving seat 5. The secondary moving seat 6 is equipped with a forward and backward screw drive mechanism 7 perpendicular to the movement direction. Both the forward and backward screw drive mechanism 7 and the main moving seat 5 are equipped with online measurement devices 8. The prior measurement device includes a 90-degree switching motor 81. The power output end of the 90-degree switching motor 81 is equipped with a frame 82. 82 includes a bushing 821 and an extension plate 822 that crosses at 90 degrees. The end of the extension plate 822 is provided with a groove plate 823, and a measuring frame 83 is provided on the back of the groove plate 823. The measuring frame 83 includes a C-shaped measuring opening 834, and the diameter of the measuring opening 834 varies between different measuring frames 83. A set of displacement sensors 84 is provided on both the top and bottom surfaces of the measuring opening 834. A contact component 85 is provided at the detection end of the displacement sensor 84, and an adjustment mechanism 853 is provided at the center of the contact component 85 to adjust its contact form with the roll 9. The bushing is driven and connected to the output shaft of the 90-degree switching motor 81 and can rotate synchronously by the same angle. The extension plate 822 and the groove plate 823 are connected by bolts, and the groove plate 823 and the extension plate 822 can be assembled with different combined lengths according to the radial length requirements of different measuring frames 83.

[0021] Specifically, the minimum measuring circle 834 of the measuring frame 83 on the lead screw drive mechanism 7 is usually smaller than the diameter of the root of the tailstock 12 because it is used to measure the minimum shaft diameter of the roll 9. The lead screw drive mechanism 7, as the carrier of the online measuring device 8, can drive the online measuring device 8 to make way for another online measuring device 8 in its initial position. Figure 4 and Figure 5As shown; the maximum circumference of the measuring frame 83 of the other online measuring device 8 is larger than the maximum shaft diameter of the roll 9, and therefore larger than the diameter of the root of the tailstock 12. This allows it to be positioned near the tailstock 12 during roll 9 hoisting, avoiding the loading range of the roll 9. By employing two sets of online measuring devices 8, each driven by a main moving seat 5 and an auxiliary moving seat 6 respectively, they can be coordinated with two sets of grinding tools operating at intervals to achieve simultaneous detection of different axial positions, which is beneficial for improving the immediacy of precision measurement operations.

[0022] Furthermore, the two sets of online measuring devices 8 provided by the present invention have four different measuring apertures 834. The rotation center of the measuring frame 83 on the main moving seat 5 is kept fixed at a distance from the center of the grinding machine spindle 11. Therefore, after the two measuring frames 83 on the main moving seat 5 complete the position switching, the concentricity of the measuring aperture 834 and the roll 9 can be guaranteed. The measuring frame 83 on the auxiliary moving seat 6 is driven by the advance and retraction screw drive mechanism 7 to approach the workpiece on the roll 9. The drive endpoint of the advance and retraction screw drive mechanism 7 can make the measuring aperture 834 of the measuring frame 83 based on it concentric with the spindle 11 of the grinding machine 1. The four different measuring apertures 834 provided by the present invention can correspond to four different shaft diameters of the same roll 9. When the workpiece enters the grinding cycle, the 90-degree switching motor 81 switches different measuring frames 83 to enter the measuring state. In order to avoid the measuring frame 83 on the auxiliary moving seat 6 from hitting the roll 9 during the switching process, the advance and retraction screw drive mechanism 7 can control the online measuring device 8 to move forward and backward by a certain distance. In this way, the two sets of online measuring devices 8 each change once, and directly enter the detection posture by switching the measuring frame 83 at 90 degrees, which reduces the frequency of direct adjustment of the displacement sensor 84. In particular, the measuring nodes of each measuring ring 834 are distributed in pairs, which helps to ensure measurement accuracy and improve processing efficiency.

[0023] To improve the processing efficiency of the roller 9 grinding machine 1, this invention uses a displacement sensor 84 as an indirect contact element and a contact assembly 85 as a direct contact element, together forming a precision adjustable device. Specifically, the contact assembly 85 includes a mounting base 851, and a contact plate 852 is centrally located on the mounting base 851, which dynamically contacts the detection end of the displacement sensor 84. The contact plate 852 includes a point contact surface 8521, a first line contact surface 8522, and a second line contact surface 8523. The lengths of the first line contact surface 8522 and the second line contact surface 8523 are different and both are tangent to the circumference of the point contact surface 8521. The surface of the contact plate 852 is parallel to the axial direction of the roller 9. The angle of the contact plate 852 is adjusted by an adjustment mechanism 853, so that the point contact surface 8521, the first line contact surface 8522, and the second line contact surface 8523 contact the top generatrix of the roller 9 according to the detection requirements. The point contact surface 8521 is used to achieve point contact with the roll 9, and can be detected point by point during the first detection process. The first line contact surface 8522 and the second line contact surface 8523 are in line contact with the top generatrix of the roll 9. During the second detection process, their detection length is appropriately lengthened and the detection accuracy is reduced. If obvious out-of-roundness or large fluctuations in roughness occur, the point contact is switched back to further reduce the detection range. This allows for rapid locking of the deviation position during the second detection process. Therefore, the contact component 85 of the present invention can realize multiple forms of contact detection, namely point contact and line contact, which can shorten the secondary detection cycle and improve processing efficiency.

[0024] Furthermore, the contact plate 852 provided by the present invention has a measuring stroke circular hole 8524 and a cross stroke hole 8525 communicating with the measuring stroke circular hole 8524 at its center. The adjusting mechanism 853 includes a rotating flap 8531, which includes a circular segment that mates with the measuring stroke circular hole 8524 and a straight segment that mates with the cross stroke hole 8525. The length of the straight segment is less than the unidirectional length of the cross stroke hole 8525. The driving end of the rotating flap 8531 is provided with a dual servo telescopic rotary electric cylinder 8532. The inner side of the mounting base 851 is provided with a clutch groove 854 for the rotating flap 8531 to quickly leave the contact plate 852. The diameter of the measuring stroke circular hole 8524 is larger than the diameter of the circular segment of the rotating flap 8531, and the difference in diameter between the two can be used as the maximum tolerance. The dual-servo telescopic rotary electric cylinder 8532 drives the rotating lobe 8531 to rotate 90 degrees through rotational action. The rotating lobe 8531 then drives the contact plate 852 to rotate 90 degrees, thus switching the contact mode of the contact plate 852. The dual-servo telescopic rotary electric cylinder 8532 then retracts the rotating lobe 8531 into the clutch groove 854 through telescopic action, rotates it back to keep its straight section vertical, and then pushes it into the contact plate 852 through telescopic action. In this way, the adjusting mechanism 853 can not only switch the contact mode as a transmission connector of the contact plate 852, but also act as a guide and tolerance component for the vertical floating of the contact plate 852, thereby converting the displacement detected by the contact plate 852 into the detection data of the displacement sensor 84, thus realizing the function of adjustable accuracy.

[0025] To improve the cooperation performance between the adjusting mechanism 853 and the contact plate 852, the mounting base 851 provided by the present invention is provided with a sealing end plate 855 at its end. A positioning groove 856 is provided between the sealing end plate 855 and the contact plate 852, which is axially movable with the sealing end plate 855. A spring 857 is provided between the positioning groove 856 and the sealing end plate 855. A plurality of braking cylinders 858 are provided at the end of the positioning groove 856, and the braking cylinders 858 cooperate with the positioning blind grooves 8526 provided on the contact plate 852. The end face of the rotating flap 8531 can protrude from the plate surface of the contact plate 852 to disengage the braking cylinders 858 from the positioning blind grooves 8526, so that the contact plate 852 can generate effective lifting displacement with the continuous rotation of the roll 9. If the rotating petal 8531 leaves the contact plate 852, its end face will completely leave the contact plate 852, causing the braking cylinder 858 to be stuck in the positioning blind groove 8526 under the pressure of the spring 857. Furthermore, the positioning groove 856 and the sealing end plate 855 only have axial displacement, without relative rotation, thus ensuring that the contact plate 852 will not rotate freely until the rotating petal 8531 returns to the inside of the contact plate 852. Therefore, the adjustment mechanism 853 provided by this invention has good cooperation performance with the contact plate 852, effectively ensuring the controllability of the contact form between the contact plate 852 and the roll 9.

[0026] To improve the compatibility of this device with different rolls 9, the measuring frame 83 provided by this invention has a mounting groove 831 at its end for mounting a displacement sensor 84. The outer side of the mounting groove 831 has a screw hole 832 for mounting a locking screw and an adjusting bolt hole 833 for mounting an adjusting bolt. The adjusting bolt connects the measuring frame 83 and the contact assembly 85. Thus, before grinding different rolls 9, the relative distance between the contact assembly 85 and the measuring ring 834 surface is controlled by the adjusting bolt, while simultaneously controlling the height of the displacement sensor 84. This ensures the reliable installation of the contact assembly 85 and allows the point contact surface 8521, the first line contact surface 8522, and the second line contact surface 8523 to establish effective contact with the roll 9, thereby improving the utilization rate of this device.

[0027] The measuring stroke of the main moving seat 5 provided by this invention is greater than that of the auxiliary moving seat 6. The online measuring device 8 on the main moving seat 5 is used to measure the longest axial surface and its left end axial surface of the roll 9, while the online measuring device 8 on the auxiliary moving seat 6 is used to measure the two-stage axial surface at the right end of the roll 9. Therefore, the total stroke of the main moving seat 5 is greater than that of the auxiliary moving seat 6. The left-hand moving grinding device 13 on the grinding machine 1 grinds the left side of the roll 9, and its working stroke is long. The working stroke of the moving grinding device 13 used to grind the right end axial surface of the roll 9 is short, so the grinding cycle of the right-hand moving grinding device 13 is less than that of the left-hand moving grinding device 13. To reduce the need for secondary starts of the moving grinding device 13, the travel speed of the two moving grinding devices 13 can be appropriately controlled. Correspondingly, the horizontal moving measurement speed of the main moving seat 5 is greater than that of the auxiliary moving seat 6. The main moving seat 5 and the auxiliary moving seat 6 are each connected to a set of lead screw mechanisms, and telescopic covers are installed in the transmission direction for protection. Regarding their power sources, they can use independent power supplies or share a common power source connected via a reduction gear. The reduction gear is installed at the ends of the two lead screw mechanisms, with the connection end between the reduction gear and the lead screw mechanism of the main moving seat 5 being the relatively high-speed end, and the connection end with the four-bar linkage of the auxiliary moving seat 6 being the low-speed end. The high and low speed ends can be reduced using pulleys and belts, or by using gear sets. Using gear sets provides better position control accuracy for the main moving seat 5 and the auxiliary moving seat 6.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A roll grinding machine with an adjustable precision device, comprising a grinding machine including a spindle and a tailstock, wherein two sets of moving grinding devices for grinding rolls at intervals are arranged between the spindle and the tailstock, and a prior measurement drive device independent of the grinding machine is arranged on one side of the grinding machine, characterized in that, The power output end of the prior measurement drive device is provided with a main moving seat and a secondary moving seat with parallel movement trajectories. The secondary moving seat is provided with a forward and backward screw drive mechanism perpendicular to the movement direction. Both the forward and backward screw drive mechanism and the main moving seat are provided with online measurement devices. The prior measurement device includes a 90-degree switching motor. The power output end of the 90-degree switching motor is provided with a frame. The frame is provided with two measuring frames connected to it and staggered at 90 degrees. The measuring frames include C-shaped measuring rings, and the diameter of the measuring rings of different measuring frames is different. A set of displacement sensors is provided on the top and bottom surfaces of the measuring rings. The detection end of the displacement sensor is provided with a contact component. The center of the contact component is provided with an adjustment mechanism for adjusting its contact form with the roll.

2. A roll grinding machine with an adjustable precision device according to claim 1, characterized in that, The contact assembly includes a mounting base, and a contact plate is provided at the center of the mounting base to dynamically contact the detection end of the displacement sensor. The contact plate includes a point contact surface, a first line contact surface, and a second line contact surface. The lengths of the first line contact surface and the second line contact surface are different and both are tangent to the circumference of the point contact surface.

3. A roll grinding machine with an adjustable precision device according to claim 2, characterized in that, The contact plate has a measuring stroke circular hole and a cross stroke hole that communicates with the measuring stroke circular hole at its center. The adjustment mechanism includes a rotating flap, which includes a circular segment that mates with the measuring stroke circular hole and a straight segment that mates with the cross stroke hole. The length of the straight segment is less than the unidirectional length of the cross stroke hole. The driving end of the rotating flap is equipped with a dual servo telescopic rotary electric cylinder.

4. A roll grinding machine with an adjustable precision device according to claim 3, characterized in that, The inner side of the mounting base is provided with a clutch groove for the rotating disc to quickly disengage from the contact plate.

5. A roll grinding machine with an adjustable precision device according to claim 4, characterized in that, The mounting base is provided with a sealing end plate at its end. A positioning groove is provided between the sealing end plate and the contact plate, which is axially movable with the sealing end plate. A spring is provided between the positioning groove and the sealing end plate. Multiple braking cylinders are provided at the end of the positioning groove. The braking cylinders cooperate with the positioning blind grooves provided on the contact plate.

6. A roll grinding machine with an adjustable precision device according to claim 1, characterized in that, The measuring frame has a mounting slot at one end for mounting a displacement sensor. The outer side of the mounting slot has a screw hole for mounting a locking screw and an adjusting bolt hole for mounting an adjusting bolt. The adjusting bolt connects the measuring frame and the contact assembly.

7. A roll grinding machine with an adjustable precision device according to claim 1 or 6, characterized in that, The measuring stroke of the main moving seat is greater than that of the auxiliary moving seat, the horizontal moving measuring rate of the main moving seat is greater than that of the auxiliary moving seat, and the main moving seat and the auxiliary moving seat share a common power source and are connected by a reduction gear.

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