HK1114147A - Drive assembly for a motorized roller tube system - Google Patents

Description

Drive assembly for motorized roller tube system

Reference to related application

【0001】 This application is related to and claims priority from U.S. application No.11/096,783, filed on 1/4/2005. The entire contents of this application are incorporated herein by reference.

Technical Field

【0002】 The present invention relates to motorized roller tube systems for winding flexible winding members such as shades, screens and the like, and more particularly to drive assemblies for motorized roller tube systems.

Drawings

【0003】 FIG. 1 is a perspective view of a motorized roller tube system including a prior drive assembly:

【0004】 FIG. 2 illustrates the motor and gear set of the prior drive assembly of FIG. 1;

【0005】 FIG. 3 is a motor curve for the motor of FIG. 2;

【0006】 FIG. 4 is a perspective view of a drive assembly for a motorized roller tube system according to the present invention;

【0007】 FIG. 5 shows the gear stages of the motor and gear set after removal from the drive assembly of FIG. 4;

【0008】 FIG. 6 is an exploded perspective view of the motor and gear set of FIG. 4;

【0009】 Fig. 7 is a motor curve for the motor of fig. 4 and 5.

Background

【0010】 Referring to FIG. 1, a motorized roller tube system 10 having a prior drive assembly 12 is shown. The motorized roller tube system 10 includes a rotatably supported roller tube 14 and a flexible member 16, such as a shade fabric, windingly received by the roller tube 14. The flexible member 16 is typically engaged with the roller tube 14 by securing one end of the flexible member 16 to the roller tube 14. There are many known methods of securing the flexible member 16 to the roller tube 14, such as using double-sided tape, or by a clip member that fits over one end of the flexible member 16 into a locking channel provided on the surface of the roller tube 14. The drive assembly 12 drives the roller tube 14 in opposite rotational directions for winding and unwinding the flexible member 16 relative to the roller tube 14. The prior drive assembly 12 includes an elongated housing 18 and a disk 20 positioned near the end of the housing 18. The puck 20 engages the interior surface of the roller tube 14 so that the drive assembly 12 drives the roller tube 14 as the puck 20 rotates.

【0011】 The prior roller tube drive assembly 12 includes a motor 22 and gear assembly 24 disposed within the housing 18 and connected to the puck 20. Shown in fig. 2 is motor 22 and gear set 24 removed from housing 18. The motor 22 of the prior drive assembly 12 is a dc motor. Referring again to fig. 1, the drive assembly 12 is housed inside the roller tube 14. In this regard, roller tube drive assemblies of this type are referred to as "internal" drive assemblies. Other known motorized roller tube systems include a drive assembly disposed outside the roller tube.

【0012】 The motor 22 includes an output shaft 23 that is driven to rotate by the motor at a rotational speed referred to as the "motor speed". The prior drive assembly 12 operated the motor at a motor speed of approximately 2000 rpm. A gear set 24 connected to the output shaft of motor 22 reduces the relatively fast input speed 2000rpm from motor 22 to a relatively slow output speed of approximately 27rpm for roller tube 14. Thus, the gear ratio of the gear set 24 of the prior drive assembly 12 is approximately 74: 1 (i.e., 2000/27).

【0013】 The motor torque capability varies with the motor speed. Thus, the motor of any motorized roller tube system must provide a torque capacity sufficient to wind the flexible member 16 onto the roller tube 14 at the operating motor speed. Referring to fig. 3, the performance characteristics of the motor 22 of the prior drive assembly 12 are graphically illustrated. This type of graph is called a "motor curve". The relationship between motor speed (given on the Y-axis) and motor torque capability (given on the X-axis) is represented by line 26. As shown, the maximum motor speed of the motor 22 is about 3150rpm, and its maximum motor torque is about 280 m-Nm. As also shown, the motor torque capability of dc motor 22 varies linearly throughout the motor speed range. In other words, the motor torque capability increases with decreasing motor speed, even at very low speeds close to zero. It should be understood that the motor torque value on speed/torque line 26 in fig. 3 represents the desired torque, rather than a fixed value of motor torque when in operation. In other words, the motor 22 is capable of operating at any torque between zero (i.e., no load condition) and the value shown on the speed/torque line 26 at a given motor speed. At an operating speed of 2000rpm, the desired torque for motor 22 is approximately 99 m-Nm.

【0014】 The efficiency of motor 22 also varies with motor speed, as shown by curve 28 in fig. 3. The efficiency, which is shown on the Y-axis along with the motor speed, is determined by reading vertically the values from the speed/torque line 26 to the efficiency curve 28. Thus, the efficiency of the motor 22 of the prior drive assembly 12 is approximately 25% at a motor operating speed of 2000 rpm. As shown, a motor efficiency of 25% is the peak efficiency of motor 22. Where the motor speed corresponding to the peak efficiency is referred to as the peak efficiency motor speed. The peak efficiency motor speed is approximately 65% of the maximum motor speed (i.e., 2000/3100).

【0015】 Although the specific values of motor speed, torque capability and efficiency vary from one dc motor to another, certain characteristics are common to all dc motors. First, the motor speed and motor torque capability vary linearly and inversely over the entire range of motor speeds including very low speeds approaching zero. Second, motor efficiency generally reaches peak efficiency at low load conditions (i.e., relatively low torque at motor speeds greater than 50% of maximum motor speed). Existing drive assemblies configure and operate the motor such that the motor operates at a low load condition near peak efficiency motor speed. As will be described in greater detail below, operating the motor in such a relatively low load condition is consistent with motor manufacturer recommended motor operation.

【0016】 The gear assembly of the known roller tube drive assembly includes planetary spur gears. The construction of planetary spur gears is economically desirable and provides an efficient transmission ratio as compared to other types of gears. However, spur gears tend to produce noise during operation, as compared to other types of gears, because the peripheral teeth make contact with each other, which can produce sound. This contact noise associated with meshing teeth is sometimes referred to as "gear slap" which increases as the speed of rotation of the meshing gear increases. Known gear sets also include gear stages having bevel gears. Helical gears include elongated helical ramps that constantly engage the ramps of other helical gears. The constant meshing of the ramps eliminates the flapping noise associated with contact between the spur gear teeth. However, helical gears tend to be less economical and efficient than spur gears.

【0017】 The gear set 24 of the prior drive assembly 12 includes three stage gears 30, 32, 34. The gear set 24 is a hybrid gear system that includes a first stage 30 having helical gears and second and third stages 32, 34 having planetary spur gears. Closest to the motor 22 is the first stage 30. Thus, the gears of the first stage 30 rotate at a relatively fast motor speed of 2000 rpm. However, the rotational speed in the second and third stages 32, 34 is stepped down from the motor speed of 2000 rpm. Thus, the hybrid configuration of the prior drive assembly 12 represents a compromise in which quieter, less efficient, more expensive helical gears are used in the relatively fast first stage 30, while efficient, less expensive but noisier planetary spur gears are used in the relatively slow second and third stages 32, 34.

Disclosure of Invention

【0018】 In accordance with the present invention, a noiseless drive assembly for a motorized roller tube system includes a motor and a gear set having a plurality of gear stages. The drive assembly is configured such that the motor is inefficiently driven at a relatively low motor speed. Preferably, the operating motor speed is below 50% of the maximum motor speed. Preferably, the efficiency at which the motor operates is less than 50% of the peak motor efficiency. Preferably, the torque of the motor at the operating motor speed is greater than 4 times the torque at the peak efficiency motor speed.

【0019】 According to one embodiment, the motor is a dc motor and one or more stages of the gear set include planetary spur gears. The noiseless drive assembly preferably provides a sound pressure level of between about 40 decibels and about 44 decibels when measured about 3 feet away from the driven end of the roller tube in an ambient environment with a sound pressure level of about 38 decibels during movement of the roller tube. Sound pressure levels of this level are considered pleasant and not distracting.

【0020】 According to one embodiment, the gear ratio of the gear set is about 20: 1 and the motor is driven at a motor speed between 0 and 1500 rpm. Most preferably, the motor speed is about 850 rpm.

【0021】 According to one embodiment, the electric machine is an alternating current machine. Preferably, the ac machine has 4 or fewer electrodes. The AC motor includes an output shaft that rotates at an operating speed of between about 750rpm and 900 rpm.

【0022】 According to one embodiment, the drive assembly is received inside a roller tube having a diameter of less than 2 inches and a maximum motor torque of the motor is greater than about 120 m-Nm.

Concrete mode of installation

【0023】 Referring to the drawings, wherein like numerals indicate like elements, there is shown in fig. 4 through 6 a roller tube drive assembly 40 according to the present invention, including a motor 42 and gear assembly 44 housed within an elongated housing 41. The drive assembly 40 of the present invention is adapted to be received within a roller tube, such as tube 14 in fig. 1, to engage the interior surface of the roller tube to drive the tube in rotation to wind or unwind a flexible member, such as a shade fabric. The receipt and engagement of the drive assembly 40 is similar to the prior drive assembly 12 described above. However, as will be described in greater detail below, the drive assembly 40 of the present invention is constructed in a novel manner to drive a particular load with a reduced roller tube diameter or with a particular roller tube diameter but with a greater load. Moreover, the new configuration produces limited noise because the roller tube motion is relatively quiet, while it is desirable to use spur gear drive throughout the gear train 44.

【0024】 The motor 42 of the drive assembly 40 is preferably a dc motor. The motor 42 has an output shaft 43 that delivers mechanical power at a certain motor speed and torque. Dc motors are highly reliable, relatively inexpensive, and can achieve the appropriate torque capability in a sufficiently small size for most roller tube applications. Dc motors include brushed and brushless dc motors. Brushed and brushless dc motors have similar torque/speed curves. However, brushless dc motors have a winding stator surrounding a permanent magnet rotor, which is the opposite arrangement to a brushed dc motor. This configuration of the brushless motor eliminates the need for motor brushes that allow current to flow through the winding rotor in a brushed motor. The stator windings of a brushless dc motor are electronically rectified with control electronics to control current flow. There are many types of brushed dc motors available today, and therefore brushed dc motors are currently preferred for economic reasons.

【0025】 Most of the noise generated by the drive assembly 40 is caused by the motor 42 and gear set 44. The noise producing components are shown in fig. 5 after removal from the remainder of the drive assembly 40 for comparison with the corresponding components of the prior art drive assembly 12 of fig. 2. The gear train 44 of the drive assembly 40, which is mounted within the roller tube 40, includes first and second gear stages 46, 48 for reducing the rotational speed from the motor 42 to a desired rotational speed for driving the rotation of the roller tube. The gears in each stage 46, 48 of the gear set 44 are planetary spur gears. As noted above, it is desirable to use planetary spur gears in all stages of the gear set 44 because spur gears are not only economical but also have a high gear ratio as compared to other types of gears, such as helical gears in the first stage of the prior art gear set 12. The planetary spur gears of the gear set 44 are preferably made of plastic.

【0026】 Referring to fig. 7, a motor curve for the motor 42 is shown. Similar to the motor curve for motor 22 of fig. 3, fig. 7 graphically illustrates various performance characteristics of motor 42, including motor speed, motor torque capability, and motor efficiency. As indicated by line 51, the motor speed and motor torque of motor 42, like motor 22, are inversely proportional to each other throughout the range of motor speeds, including very low speeds approaching zero. The maximum motor speed of the motor 42 is approximately 4200rpm and the maximum motor torque capability is approximately 122 m-Nm. As shown by efficiency curve 53, the motor efficiency of motor 42 reaches a peak of approximately 75% when operating at a speed of approximately 3700 rpm.

【0027】 The motor curve of fig. 7 includes the manufacturer's recommended operating range as indicated by the shaded area 55 in the figure. As shown, the manufacturer's recommended operating range for the motor 42 includes motor speeds corresponding to relatively low load conditions (i.e., relatively high motor speeds and relatively low motor torques). Not surprisingly, the manufacturer's recommended operating range includes the peak efficiency motor speed of 3700 rpm. As discussed above, the motors of prior roller tube drive assemblies operate under low load conditions as recommended by the manufacturer. Specifically, manufacturers of electric machines 42 recommend that the electric machines operate at machine speeds greater than about 3200rpm, which is a speed range between about 76% and 100% of the maximum machine speed of electric machine 42, which is 4200 rpm. Also similar to the motor 18, the recommended operating range for the motor 42 includes a peak efficiency motor speed of 3700 rpm.

【0028】 Intuitively, it would appear that it is preferable in the prior art to operate the motor of the roller tube drive assembly within the manufacturer's recommended limits in accordance with conventional practice. As described above, the recommended operating range includes peak efficiency motor speeds. Thus, operating the motor within the recommended range enables the motor to operate efficiently. In addition, the relatively low load condition (i.e., relatively low torque) associated with the recommended range is used to limit overheating damage, which may be caused by high load operation of the motor, thereby extending motor life.

【0029】 However, the drive assembly 40 is not conventionally configured to operate the motor 42 within the manufacturer's recommended range. Instead, the motor 42 of the drive assembly 40 is preferably operated in a high load condition (i.e., relatively high torque), i.e., within a motor speed range indicated by shaded area 57 in fig. 7. As shown, the preferred operating range 57 includes a greater range of motor speeds between 0rpm and about 1500 rpm. The upper limit of the preferred operating range, 1500rpm, is approximately 36% of the maximum motor speed of 4200rpm of motor 42. Most preferably, the drive assembly 40 operates the motor 42 at a speed of approximately 850rpm, which is only approximately 20% of the maximum speed. The motor torque of the motor 42, as indicated by line 51 in FIG. 7, is approximately 98m-Nm when operated at 850 rpm. As shown by curve 53, the motor efficiency of the motor 42 is approximately 19% when it is operating at the preferred 850rpm speed. The motor efficiency is only about one-quarter of the peak efficiency of the motor 42 (i.e., 19/75). The drive assembly 40 of the present invention is configured to operate the motor 42 at motor speeds well outside of the recommended range, in which case the motor is very inefficient.

【0030】 The 98m-Nm torque capability provided by motor 42 when operated at a motor speed of 850rpm is substantially equivalent to the 99m-Nm torque provided by motor 22 of the prior art drive assembly 12 when operated at a motor speed of 2000 rpm. However, the diameter of motor 22 is 1.65 inches, while the diameter of motor 42 is only about 1.22 inches. Thus, by operating inefficiently outside the recommended operating range, the present invention provides similar torque capability for driving similar loads while allowing for a reduction in motor diameter. By reducing the motor diameter, the correspondingly provided roller tube diameter is correspondingly reduced. It is aesthetically desirable to limit the roller tube diameter to avoid the bulky appearance of the mount. It should be appreciated that instead of reducing the motor diameter, the present invention may be utilized to increase the torque capability of a given motor to drive a load.

【0031】 The motor 22 of the prior drive assembly 12 is approximately 2.7 inches in length. Thus, the length to diameter ratio (i.e., length to diameter) of motor 22 is approximately 1.64 (i.e., 2.7/1.65). This aspect ratio is typical for standard torque motors. The motor 42 of the drive assembly 40 of the present invention is also approximately 2.7 inches in length. Thus, the aspect ratio of the motor 42 is about 2.21 (i.e., 2.7/1.22). The effect of the increased aspect ratio of the motor 42 can be seen by comparing figures 2 and 5. It is known that for a motor its torque varies in proportion to BID2L, where B is the magnetic flux, I is the current, and D and L are the diameter and length of the motor, respectively. Therefore, the motor torque can be increased by increasing any of B, I, D, or L. The motor 42 of the drive assembly of the present invention is considered a "high" torque motor because of the increased aspect ratio compared to a standard torque motor. Increasing the torque of the motor 42 by increasing the aspect ratio (i.e., increasing the length) partially compensates for the torque that is reduced by decreasing the diameter. Of course, since the diameter is squared in the above relationship (i.e., BID2L), decreasing the diameter has a greater effect on torque than increasing the length. The present invention therefore also provides increased torque by operating the smaller diameter motor under the high load conditions described above in connection with the preferred range 57.

【0032】 As described above, the 98m-Nm torque provided by the motor 42 when operated at a motor speed of 850rpm is substantially equivalent to the 99m-Nm torque provided by the motor 22 of the prior drive assembly 12 when operated at a motor speed of 2000 rpm. However, the present invention is not limited to any particular torque. Thus, it is contemplated that the drive system may be configured to include a smaller diameter motor having a reduced torque as compared to motor 42, such a motor being usable within a smaller diameter roller tube. For example, a motor having a maximum torque of between 50m-Nm and 70m-Nm can be used to drive roller tubes having a diameter of less than about 1.625 inches.

【0033】 As mentioned above, planetary spur gears are the preferred gear type because of their economy and high gear ratio, but tend to produce undesirable noise when driven by the relatively high motor speeds of existing drive assemblies. However, the present invention allows the use of spur gears in each stage of the gear set 44 by reducing the motor speed to approximately 850rpm without excessive noise generation in the first stage 46 due to gear slapping. As described above, the required gear ratio of gear set 44 is also reduced to approximately 20: 1 when the motor speed is reduced to 850 rpm. As a result, it becomes possible to reduce the number of gear stages from 3 stages to 2 stages. Thus, the reduction in the number of stages reduces the total number of gears in the assembly to further reduce the noise generated by the gear set.

【0034】 It is desirable for the drive assembly of the motorized roller tube system to be capable of variable speed control of the drive assembly motor. Such variable speed control is desirable to vary the effective winding radius to cause the flexible member to be wound onto the roller tube at a substantially constant speed of movement. As the flexible member is wound onto the tube, the flexible member forms a layer (or "wrap") to change the effective radius at which the flexible member is received or released by the roller tube. Thus, if the roller tube is driven at a constant rotational speed, the speed of movement of the flexible member (sometimes referred to as the "line speed" or "fabric speed") will vary as the effective winding radius changes. It will be appreciated that the rotational speed needs to be reduced as the flexible member is wound onto the tube to maintain a constant fabric speed, and therefore the rotational speed at which the roller tube is driven is at a maximum at or near a position at which the flexible member is fully unwound from the roller tube (i.e., a "fully reduced" or "fully closed" position). In addition, the amount of material that is wound onto the tube is minimized when the flexible member is in the fully lowered position of the flexible member, thereby minimizing the amount of noise attenuation that the flexible member provides to the roller tube in this position. Thus. The sound level produced by the motorized roller tube system is maximized when the drive assembly drives the roller tube at or near the fully lowered position of the flexible member.

【0035】 The present invention provides a drive assembly 40 that desirably includes planetary spur gears in each stage of its gear set 44 while also limiting the drive assembly from generating noise. A motorized roller tube system including a drive assembly 40 housed within a 1.625 inch diameter roller tube is used to drive a typical applied load of about 8.1 in-lb (i.e., 10 pounds of flexible member having a 0.81 inch radius). The noise level generated by the motorized roller tube system was measured at a distance of approximately 3 feet from the driven end of the roller tube using an acoustic pressure gauge. In an ambient environment of about 38 db, the sound pressure level generated by the motorized roller tube system is about 43 db when the drive assembly 40 drives the roller tube at or near the fully lowered position of the flexible member (i.e., where the sound pressure level generated by the motorized shade assembly is at a maximum). An ambient level of 38 db corresponds to the sound pressure level in a relatively quiet office, such as a private office with doors closed. Sound pressure levels between about 40-44 db produced by a motorized roller tube system so configured are not considered disturbing or even pleasant. The sound level produced by the present drive assembly having planetary spur gears driven at speeds well below the motor manufacturer's recommended operating range is advantageous over the sound level produced by existing drive assemblies having planetary spur gears driven at the recommended faster motor speeds. Existing motorized roller tube systems include systems that generate sound pressure levels in excess of 50 db at about 3 feet in an ambient environment of about 38 db. It is considered that it is disturbing or even annoying to be in an environment with sound pressure levels exceeding 50 db.

【0036】 The gear set 44 described above includes two gear stages 46, 48. But the number of gear stages is not critical. Thus, the drive assembly according to the invention may in the above described embodiments comprise more than two stages. However, as described above, reducing the number of gear stages is expected to reduce the total number of gears in the gear set, and correspondingly, reduce gear rattle noise.

【0037】 As described above, it is counter-intuitive for the drive assembly 40 to operate the motor 42 inefficiently under high load conditions. In addition to inefficient motor operation, continued operation of the motor in the high load torque condition associated with the preferred operating range 57 may overheat the motor resulting in a shortened motor life. However, the motor of motorized roller tube systems is typically not continuously operated. In a typical motorized roller tube system, such as a window shade, the shade fabric is raised in the morning and lowered in the evening, and it is also possible to adjust to other positions several times during different times of the day. Thus, except for the most unusual case, inefficient operation of the drive motor 42 does not significantly affect the life of the motor. However, to protect the motor 42, it is contemplated that the drive assembly 40 may be configured to track the run time of the motor 42. The motor 42 is then shut down if it runs out of time for a specified period of time that may be detrimental to the motor if allowed to continue to run. Alternatively, the state of the motor may be monitored using a thermocouple, thermistor, temperature sensor, or other suitable sensing device based on the temperature of the motor or associated components or the temperature of the surrounding area.

【0038】 The construction of the drive assembly 40 will now be discussed in detail in conjunction with FIG. 4. The elongated tubular housing 41 defines an interior that houses a drive motor 42 and a gear train 44. The drive assembly 40 preferably includes an electronic drive unit ("EDU") 50 for controlling the operation of the motor 42. The EDU controller 50 includes a printed circuit board for arranging control circuitry (not shown) of the controller 50. The controller 50 can be configured to track the run time of the motor 42 in the manner described above and shut down the motor 42 in the event that excessive use of the motor 42 for a given period of time may damage the motor 42. The EDU controller 50 includes a bearing sleeve 54 and a bearing spindle 56 adjacent one end of the housing 41. Electronic drive units for motorized roller tube systems are known and need not be described further.

【0039】 The drive assembly 40 includes a drive disk 58 disposed adjacent an end of the housing 41 opposite the EDU bearing sleeve 54 and the spindle 56. The drive disc 58 is connected to a disc shaft 60, wherein the disc shaft 60 is rotatably supported with respect to the housing 41 of the drive assembly 40 by a drive bearing 62. The disc shaft 60 is connected to the gear set 44 of the drive assembly 40 so that the drive motor 42 drives the drive disc 58 to rotate. The drive puck 58 has longitudinal grooves on its outer surface to facilitate engagement between the outer surface of the puck 58 and the inner surface of the roller tube when the drive assembly is installed in the roller tube. The drive assembly 40 is adapted to be mounted within a roller tube such that the EDU bearing sleeve 54 and spindle 56 are disposed near the end of the roller tube. The drive assembly 40 also includes a brake 64 having a brake input 66, a brake output 68, and a brake spindle 70. The brake 64 has an interior that receives the disc shaft 60. The brake 64 is adapted to engage the disc shaft 60 to prevent relative rotation between the motor 42 and the drive disc 58. Engagement of the brake 64 prevents the flexible member from unwinding due to the load applied to the roller tube by the unwound portion of the flexible member and the hembar on the flexible member, thereby maintaining the flexible member in the selected position. Brakes for roller tube drive assemblies are known and need not be further described.

【0040】 Referring to fig. 6, the motor 42 and gear set 44 of the drive assembly 40 are shown in detail. The gear set 44 includes a ring gear 72 mounted within a ring gear cover 74. The motor adapter 76 is disposed between the motor 42 and the ring gear cover 74, and engages with an end of the ring gear cover 74. The ring gear cover 74 includes a projection 78, the projection 78 being received in a correspondingly shaped recess 80 of the motor adapter 76 to limit relative rotation therebetween. The ring gear cover 74 also includes an end fitting 82 that is received by the brake spindle 70.

【0041】 The gear set 44 includes a sun gear 45 connected to the output shaft 43 of the motor 42, the sun gear 45 rotating with the output shaft 43. Preferably, the sun gear 45 is stamped on the output shaft 43. Each of the first and second stages 46, 48 of the gear set 44 includes three spur planet gears that mesh with longitudinal teeth 96 formed on the inner surface of the ring gear 72. The sun gear 45 engages the spur gear of the first stage 46 so that the spur gear of the first stage 46 is driven for rotation by the sun gear 45 at the motor speed. The spur gears of the first stage 46 are rotatably mounted on pins 90 of the center bracket 88. The spur gears of the second stage 48 are rotatably mounted on pins 94 of the hexagonal carrier 92. The gear set 44 also includes a second stage adapter 102, the second stage adapter 102 including a hexagonal head 104 that is received by the hexagonal slot of the hexagonal bracket 92 and a slot 106 on the opposite side of the hexagonal head 104 that receives the end of the drive disk shaft 60. As the second stage 48 drives the hexagonal carrier 92, the second stage adapter 102 transmits the rotation of the hexagonal carrier 92 to the drive puck 58.

【0042】 The controller 50 of the drive assembly 40 preferably provides variable speed control of the rotational speed of the motor 42. Variable speed control in a roller tube drive assembly is desirable to adjust the speed at which the flexible member is wound onto the roller tube so that the speed of movement of the flexible member (referred to as the "line speed" or "fabric speed") is substantially constant. Such a control system is disclosed in U.S. patent application No.10/774,919 entitled "control system for uniform movement of multiple roller shades" filed on 2004, 2/9, which is hereby incorporated by reference in its entirety. Because the flexible member is to be wound onto the roller tube, the flexible member material is processed to form a layer (or "wrap"). The radius of the fabric layer received or released by the roller tube is changed. Thus, if the roller tube is driven at a constant rotational speed, the speed of the flexible member tends to increase as the flexible member is wound onto the roller tube. It is known to control the motor speed of an ac motor by controlling the voltage supplied to the motor using pulse width modulation. U.S. patent No.5,848,634, incorporated herein by reference, discloses a motorized roller tube system that utilizes pulse width modulation to vary the speed of the motor.

【0043】 The motor 42 of the drive assembly is a dc motor, preferably a brushed dc motor. It may be preferable for some applications, particularly when the load to be driven by the motor is relatively large, to have an ac induction motor as opposed to a dc motor. This situation may arise, for example, where a single motor drives multiple roller tubes arranged in a tail-to-tail fashion. For variable speed control for an ac induction motor, the frequency and voltage supplied to the motor are adjusted simultaneously instead of just adjusting the voltage. An ac induction motor is typically wound with a set of stator windings, each driven by an ac voltage wave. Typically, three separate windings driven by three phases of an ac voltage wave are spaced around the outer circumference of the motor stator. The phase shift of the drive voltage wave sets the rotation range in the rotor part of the motor. The reaction forces between the induced field in the rotor and the field in the stator cause a net moment acting on the rotor. The rotational speed of the rotor is related to the frequency of the drive wave and the number of electrodes generated by the stator winding structure. This relationship is illustrated by the following equation: n-120 xf/P, where n is the rotor speed in rpm, F is the drive voltage frequency in Hertz, and P is the number of electrodes.

【0044】 Commercially available ac induction motors typically comprise 2 or 4 poles. Such a configuration facilitates the production of the stator winding. Ac induction motors with 2 or 4 poles are typically operated at rated speeds of 3600rpm and 1800rpm, respectively, when the drive voltage wave is 60 Hz. In order for these types of motors to operate at speeds of approximately 750 to 900rpm, the operating frequency needs to be reduced. This is achieved by the control of the frequency by the inverter circuit. For example, a class 4 ac induction motor needs to be operated with a drive frequency of about 25Hz to run at a rotor speed of about 750 rpm.

【0045】 As mentioned above, the drive assembly 40 of the present invention is adapted to be received within a rotatably supported roller tube, such as the roller tube 14 shown in FIG. 1. It should be understood, however, that the present invention is not limited to use within a cylindrical tube. Thus, the rotatably supported tube may be any elongated member that can be rotatably supported and that is adapted to receive a flexible member in a wound manner. Thus, the roller tube may have a non-circular cross-section, such as hexagonal or octagonal. Non-symmetrical shapes, such as oval, are also conceivable non-circular cross-sections.

【0046】 The flexible member wound by the roller tube system incorporating the drive assembly of the present invention may comprise a curtain, screen, curtain or the like for blocking or reflecting or partially blocking or partially reflecting light. The flexible member may also be formed from paper, cloth, or any type of fabric. Examples of flexible members include window shades, screens for projectors including television projectors, curtains for blocking or partially blocking light from entering or reflecting light, curtains for concealing or protecting objects.

【0047】 The foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.

【0048】 In the appended claims, the term "flexible member" should be interpreted broadly as including any member that can be wound to block or reflect, or partially block or reflect, light. Non-limiting examples of flexible members include window shades, screens and curtains.

Claims (32)

1. A motorized roller tube system, comprising:

a rotatably supported roller tube;

a flexible member engaged with the roller tube to wind the roller tube into receiving relation with the flexible member;

a motor, the output shaft of which rotates at a certain motor speed;

a gear set connected to an output shaft of the motor, whereby the gear set is driven by the motor, the gear set including a plurality of gear stages adapted to reduce an output rotational speed relative to a rotational speed of the motor;

a pipe coupling member connected to the gear train such that the pipe coupling member rotates at the reduced rotational speed output by the gear train, the pipe coupling member adapted to engage the roller pipe such that the roller pipe rotates at the output rotational speed of the gear train;

a controller coupled to the motor for controlling the motor to wind or unwind the flexible member relative to the roller tube during movement between its fully closed and fully open positions,

wherein during movement of the flexible member the controller causes the motor to operate at an operating speed that is less than 50% of the maximum motor speed that the motor can achieve.

2. The motorized roller tube system according to claim 1, wherein the motor has a motor torque greater than 50% of a maximum motor torque during movement of the flexible member.

3. The motorized roller tube system according to claim 1, wherein the motor is a dc motor.

4. The motorized roller tube system according to claim 1, wherein at least one stage of the gear set comprises a planetary spur gear.

5. The motorized roller tube system according to claim 4, wherein the gear set comprises two stages having planetary spur gears.

6. The motorized roller tube system according to claim 1, wherein the overall gear ratio of the gear set is about 20: 1.

7. The motorized roller tube system according to claim 1, wherein the operating motor speed is between zero and about 1500rpm during the movement of the flexible member.

8. The motorized roller tube system according to claim 7, wherein the motor speed is approximately 850rpm when the flexible member is being moved from the fully lowered position.

9. The motorized roller tube system according to claim 1, wherein the roller tube has a diameter of less than about 2 inches, and wherein the motor is a dc motor having a maximum motor torque between 100m-Nm and 150 m-Nm.

10. The motorized roller tube system according to claim 1, wherein the motor, gear train, and tube coupling are received within the roller tube.

11. A motorized roller tube system, comprising:

a rotatably supported roller tube for windingly receiving the flexible member, the roller tube defining an interior;

a DC motor received within the interior of the drum tube;

a gear set received inside the roller tube, the gear set including planetary spur gears and having an overall gear ratio of about 20: 1;

the motor includes an output shaft coupled to the gear set and rotating at an operating motor speed between about 500rpm and about 1000rpm,

the motorized roller tube system produces a maximum sound pressure level of between 40 and 44 decibels in an ambient environment with a sound pressure level of about 38 decibels when the flexible member is being moved from the fully lowered position, at a distance of about 3 feet from the driven end of the roller tube.

12. The motorized roller tube system according to claim 11, wherein the gear set comprises two planetary spur gear stages.

13. The motorized roller tube system according to claim 11, wherein the motor speed is approximately 850rpm and the motor torque at the operating motor speed is at least 50% of the maximum motor torque.

14. The motorized roller tube system according to claim 11, wherein the roller tube has a diameter of less than 2 inches and the motor has a maximum motor torque of between 100m-Nm and 150 m-Nm.

15. A motorized roller tube system, comprising:

a rotatably supported roller tube for windingly receiving the flexible member;

the output shaft of the direct current motor rotates at the rotating speed of a working motor; and

a gear set connected to an output shaft of the motor such that the gear set is driven by the motor, the gear set including a plurality of gear stages adapted to reduce an output rotational speed relative to a rotational speed of the motor;

the motor has an efficiency that varies with the operating motor speed, the efficiency including a peak efficiency associated with a peak efficiency operating speed, wherein the efficiency associated with the operating motor speed is less than 50% of the peak efficiency during movement of the flexible member.

16. The motorized roller tube system according to claim 15, wherein the efficiency related to the operating motor speed during movement of the flexible member is less than 25% of peak efficiency.

17. The motorized roller tube system according to claim 15, wherein the gear set comprises a planetary spur gear.

18. The motorized roller tube system according to claim 15, wherein the operating motor speed is between zero and about 1500rpm during the movement of the flexible member.

19. The motorized roller tube system according to claim 17, wherein the gear train has a gear ratio of about 20: 1.

20. A motorized roller tube system, comprising:

a rotatably supported roller tube for windingly receiving the flexible member;

a DC motor having an output shaft rotating at a motor speed, the motor having a torque and efficiency that varies with the motor speed;

a gear set connected to an output shaft of the motor such that the gear set is driven by the motor, the gear set including a plurality of gear stages adapted to reduce an output rotational speed relative to a rotational speed of the motor;

the motor has a peak efficiency and an associated torque at a peak efficiency motor speed, wherein the motorized roller tube system operates the motor at a working motor speed at which the associated torque is at least 4 times greater than the torque at the peak efficiency motor speed.

21. The motorized roller tube system of claim 20, wherein the motor efficiency at operating motor speeds is less than 25% of peak efficiency.

22. The motorized roller tube system according to claim 20, wherein the motor is controlled by a motor speed controller, the motor being controlled to operate at an operating motor speed between about 750rpm and about 950 rpm.

23. A motorized roller tube system, comprising:

a rotatably supported roller tube for windingly receiving the flexible member, the roller tube defining an interior;

an AC motor received within the interior of the drum tube;

a gear assembly received inside the roller tube, the gear assembly including planetary spur gears and having an overall gear ratio of about 20: 1;

an AC motor controller;

the motor includes an output shaft coupled to the gear set and rotating at an operating motor speed between about 750rpm and about 900 rpm;

in an ambient environment with a sound pressure level of about 38 db, the motorized roller tube system generates a sound pressure level of between 40 db and 44 db at a distance of about 3 feet from the driven end of the roller tube.

24. The motorized roller tube system according to claim 23, wherein the ac motor is wound with 4 or fewer poles.

25. The motorized roller tube system according to claim 23, wherein the gear set comprises two planetary spur gear stages.

26. The motorized roller tube system according to claim 23, wherein the operating motor speed is about 850rpm, and wherein the motor torque at the operating motor speed is at least 50% of the maximum motor torque.

27. The motorized roller tube system according to claim 26, wherein the motor torque at the operating motor speed is at least 75% of the maximum motor torque.

28. The motorized roller tube system according to claim 23, wherein the roller tube has a diameter of less than 2 inches and the motor has a maximum motor torque of greater than about 120 m-Nm.

29. The motorized roller tube system according to claim 23, wherein the ac motor controller provides a drive signal to the motor, the drive signal comprising a controllable fundamental frequency.

30. The motorized roller tube system according to claim 29, wherein the controllable fundamental frequency is less than about 30 Hz.

31. The motorized roller tube system according to claim 29, wherein the controllable fundamental frequency is less than about 15 Hz.

32. The motorized roller tube system according to claim 1, wherein the roller tube has a diameter of less than about 1.625 inches, and wherein the motor is a dc motor having a torque capability of between 50n-Nm and 75m-Nm.