Concrete vibrator

Abstract

A concrete vibrator is disclosed that includes a housing having a motor housing portion extending along a longitudinal axis and a handle portion extending transverse to the longitudinal axis and spaced apart from the motor housing portion such that an opening is defined between the handle portion and the motor housing portion. The concrete vibrator further comprises a trigger. A brushless DC electric motor positioned within the motor housing portion; a battery pack configured to provide electrical power to the electric motor to drive the motor; and an electronic processor electrically connected with the motor and the battery pack. The electronic processor is configured to closed-loop regulate electrical power to the motor to maintain the motor operating at a speed setpoint. The concrete vibrator also includes a vibrator head configured to receive torque from the motor, thereby vibrating the vibrator head.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to co-pending U.S. Provisional Application No. 63 / 276,719, filed on November 8, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The utility model relates to a power tool, and more particularly to a concrete vibrator. Background Art

[0004] Concrete vibrators are typically used to spread poured concrete around structures (such as rebar) during construction operations. Such concrete vibrators are typically powered by internal combustion engines, which may be difficult for operators using concrete vibrators to carry when on site. Utility Model Content

[0005] In one aspect, the utility model provides a concrete vibrator, which includes a housing, the housing including a motor housing portion extending along a longitudinal axis and a handle portion extending transversely to the longitudinal axis and spaced apart from the motor housing portion, thereby defining an opening between the handle portion and the motor housing portion. The concrete vibrator also includes: a trigger located in the opening, behind the motor housing portion, and extending from the handle portion of the housing; a brushless DC electric motor, the electric motor is positioned in the motor housing portion; a battery pack, the battery pack is configured to provide electric power to the electric motor to drive the motor; and an electronic processor, the electronic processor is electrically connected to the motor and the battery pack. The electronic processor is configured to close-loop regulate the electric power to the motor to maintain the motor operating at a speed set point. The concrete vibrator also includes a vibrator head, the vibrator head is configured to receive torque from the motor to vibrate the vibrator head.

[0006] In some aspects, the trigger is configured as a variable speed trigger for outputting an electrical signal to the electronic processor that is proportional to the extent to which the trigger is depressed to change the speed of the motor.

[0007] In some aspects, the concrete vibrator further includes a flexible shaft having a first end coupled to the motor and an opposite second end coupled to the vibrator head, wherein the flexible shaft is configured to transfer torque from the motor to the vibrator head.

[0008] In another independent aspect, the utility model provides a housing, the housing comprising a motor housing portion, a motor positioned in the motor housing portion, a power source configured to provide power to the motor, and a whip assembly. The whip assembly is coupled to the motor at one end and to a vibrator head at an opposite end, the vibrator head being configured to receive torque from the motor through the whip assembly and vibrate the vibrator head, the whip assembly comprising a flexible shaft coupled to the motor, a sheath surrounding the shaft, and a device for inhibiting deflection of the flexible shaft within the sheath.

[0009] In another aspect, the utility model provides a method of operating a concrete vibrator. The method includes: sensing motor feedback indicating the position, speed or acceleration of a rotor of an electric motor; and outputting a signal indicating the motor feedback information to an electronic processor. The method further includes: transmitting current to the motor through the electronic processor and via closed-loop control based on the motor feedback information to maintain the motor operating at a speed set point. The method also includes: transmitting torque from the motor to a vibrator head of the concrete vibrator to vibrate the vibrator head.

[0010] Other features and aspects of the present invention will become apparent by considering the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a stereoscopic view of a concrete vibrator according to an embodiment of the utility model.

[0012] Figure 2 yes Figure 1 Side view of a concrete vibrator.

[0013] Figure 3 yes Figure 1 The drive unit of the concrete vibrator is along Figure 2 An enlarged side view taken along section line 3-3 in FIG.

[0014] Figure 4 The drive unit is along Figure 1 A cross-sectional view taken along section line 4-4 in FIG.

[0015] Figure 5 yes Figure 1 The vibrator head of the concrete vibrator is along Figure 1 A cross-sectional view taken along section line 5-5 in FIG.

[0016] Figure 6 The vibrator head is Figure 5 Magnified view of area 6-6.

[0017] Figure 7 The vibrator head is Figure 5 Magnified view of area 7-7.

[0018] Figure 8 yes Figure 1 Simplified block diagram of a concrete vibrator.

[0019] Fig. 9 is a cross-sectional view of a concrete vibrator including an alternative whip assembly.

[0020] Fig.10 is a cross-sectional view of a concrete vibrator including another alternative whip assembly.

[0021] Before explaining any embodiment of the utility model in detail, it should be understood that the application of the utility model is not limited to the details of the component construction and arrangement set forth in the following description or illustrated in the following drawings. The utility model can have other embodiments and can be practiced or executed in a variety of different ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be regarded as limiting. DETAILED DESCRIPTION

[0022] Figure 1 and Figure 2 The concrete vibrator 10 is illustrated and includes a housing 14, a power unit (e.g., a brushless DC electric motor 18) positioned within the housing 14, and a battery pack 22 carried on the housing 14 to provide power to the electric motor 18. In some embodiments, the battery pack 22 and the motor 18 may be configured to operate at a nominal voltage of 18V. Figure 3 The housing 14 includes a motor housing portion 14a extending along the longitudinal axis 24 and a handle portion 14b extending transverse to the longitudinal axis 24 and spaced apart from the motor housing portion 14a, thereby defining an opening 14c between the handle portion 14b and the motor housing portion 14a.

[0023] like Figure 3 , the handle portion 14b is spaced apart from the motor housing portion 14a along the longitudinal axis 24. The handle portion 14b is connected to the motor housing portion 14a by the connecting portions 54, 58 such that an opening 14c is defined by the housing 14 between the connecting portions 54, 58, the motor housing portion 14a, and the handle portion 14b. In the illustrated embodiment, the connecting portions 54, 58 extend from respective ends of the handle portion 14b in an oblique direction relative to the longitudinal axis 24 to converge at the motor housing portion 14a. In this manner, a user can extend a hand through the opening 14c to grasp the handle portion 14b of the concrete vibrator 10.

[0024] like Figure 4, the concrete vibrator 10 further includes a flexible shaft 26 extending from the housing 14 and a vibrator head 28 connected to one end of the shaft 26. As explained in further detail below, the shaft 26 receives torque from the motor 18. The torque is transferred to the vibrator head 28, causing it to vibrate. In the illustrated embodiment, the flexible shaft 26 is received within the sheath 27. In some embodiments, the flexible shaft 26 is cylindrical in shape and the sheath 27 is annular in shape. In some embodiments, the cross-sectional shape of the flexible shaft 26 and the sheath 27 can be substantially circular. In other embodiments, the shaft 26 and / or the sheath 27 can be non-circular in shape.

[0025] Further references Figure 3 The concrete vibrator 10 includes a trigger 30 that extends from the handle portion 14b into the opening 14c so that the trigger is grasped by the user when the handle portion 14b is grasped. The trigger 30 is biased toward the extended position ( Figure 3 ), in which extended position, no electrical power is delivered to the motor 18, thereby deactivating the motor 18 or maintaining the motor 18 in its non-rotating deactivated state. The trigger 30 is pulled against its bias to deliver electrical power to the motor 18, thereby activating the motor 18 and causing it to rotate at a predetermined speed (e.g., a speed set point).

[0026] In some embodiments of the concrete vibrator 10, the trigger 30 may be a variable speed trigger that allows the motor 18 to rotate at a variable speed depending on the degree to which the trigger 30 is depressed. In some embodiments, the handle portion 14b may be provided with markings (not shown) adjacent to the trigger 30 that indicate the speed at which the motor 18 rotates when the trigger 30 is depressed along the longitudinal axis 24. Additionally or alternatively, the trigger 30 may include (e.g., at least two) discrete or perceptible trigger positions (i.e., coinciding with a stop, mechanical lock, or block) when the trigger 30 is depressed a certain amount for different motor 18 speeds. In an example trigger 30 that includes discrete or perceptible trigger positions, the trigger 30 may be movable between a first operating position in which the motor 18 is driven at a first non-zero desired speed and a second operating position in which the motor 18 is driven at a second non-zero desired speed that is different from the first non-zero desired speed.

[0027] A single user can operate the concrete vibrator 10. The user can grasp the handle portion 14b with one hand and use the index finger to depress the trigger 30 and operate the motor 18, thereby causing the vibrator head 28 to vibrate. The user can hold the flexible shaft 26 or the vibrator head 28 with the other hand to position the vibrator head 28 in wet concrete.

[0028] Figure 6 and Figure 7The vibrator head 28 is illustrated in detail. Specifically, the vibrator head 28 includes an outer shell having a connecting portion 82 on one side of a body portion 86 and a head portion 90 on an opposite side of the body portion 86. The head portion 90 and the connecting portion 82 are press-fitted to the body portion 86 or otherwise mechanically connected to the body portion. The vibrator head 28 also includes an eccentric shaft 94, the opposite ends of which are rotatably supported by corresponding radial bearing pairs 98, 102, 106, 110 positioned within the body portion 86. The eccentric shaft 94 receives torque from the flexible shaft 26, thereby rotating the eccentric shaft 94. The eccentric shaft 94 is configured to vibrate the vibrator head 28 when receiving torque from the flexible shaft 26.

[0029] like Figure 6 As shown, the vibrator head 28 includes a coupling 114 interconnecting the eccentric shaft 94 and the flexible shaft 26. The vibrator head 28 further includes a lip seal 118 located between the coupling 114 and the bearings 98, 102 to inhibit penetration of wet concrete or other fluids into the body portion 86. A seal retainer 122 is radially disposed between the lip seal 118 and the body portion 86 to maintain the radial and longitudinal position of the lip seal 118 relative to the eccentric shaft 94.

[0030] refer to Figure 4 The concrete vibrator 10 further includes a power printed circuit board 122 that provides electrical power to the motor 18 and a control printed circuit board 126 that provides control signals to the power printed circuit board 122. The power printed circuit board 122 is mounted to the heat sink 20 on the motor 18 and includes a field effect transistor (FET) and a rotor position sensor 134 (e.g., a Hall effect sensor array, see Figure 8 ).

[0031] Figure 8is a simplified block diagram of a concrete vibrator 10 according to an example embodiment. In the illustrated example, the concrete vibrator 10 includes an electronic processor 42, a memory 44, a battery pack 22, a power switch network 46 (including FETs), a rotor position sensor 134, and a trigger 30. In some embodiments, the electronic processor 42 is implemented as a microprocessor with a separate memory (e.g., memory 44). In other embodiments, the electronic processor 42 may be implemented as a microcontroller (with memory 64 on the same chip). In other embodiments, the electronic processor 42 may be implemented using multiple processors. In addition, the electronic processor 42 may be implemented in part or in whole as, for example, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc., and the memory 44 may not be required or may be modified accordingly. The memory 44 stores instructions executed by the electronic processor 42 for implementing the functions of the concrete vibrator 10 described herein. The memory 44 includes a read-only memory (ROM), a random access memory (RAM), other non-transitory computer-readable media, or a combination thereof.

[0032] The power switch network 46 enables the electronic processor 42 to control the operation of the motor 18. Generally, when the trigger 30 is pressed, current is supplied from the battery pack 22 to the motor 18 via the power switch network 46. When the trigger 30 is not pressed, current is not supplied from the battery pack 22 to the motor 18. In some embodiments, the amount that the trigger 30 is pressed is related to or corresponds to the desired rotational speed of the motor 18 (i.e., closed-loop speed control). In other embodiments, the amount that the trigger 30 is pressed is related to or corresponds to the desired torque (i.e., open-loop speed control).

[0033] In response to the electronic processor 42 receiving the drive request signal from the trigger 30, the electronic processor 42 enables the power switch network 46 to provide power to the motor 18. Through the power switch network 46, the electronic processor 42 controls the amount of current available to the motor 18, thereby controlling the speed and torque output of the motor 18. The power switch network 46 includes a plurality of FETs, such as a six-FET bridge that receives a pulse width modulation (PWM) signal from the electronic processor 42.

[0034] The rotor position sensor 134 is coupled to the electronic processor 42. The rotor position sensor 134 includes, for example, a quadrature encoder attached to the motor 18, a plurality of Hall effect sensors, and the like. The rotor position sensor 134 outputs a signal representing motor feedback information to the electronic processor 42, such as an indication (e.g., a pulse) when the magnet of the rotor of the motor 18 rotates across the surface of the Hall sensor. Based on the motor feedback information from the rotor position sensor 134, the electronic processor 42 can determine the position, speed, and acceleration of the rotor. In response to the motor feedback information and the signal from the trigger 30, the electronic processor 42 transmits a control signal to control the power switch network 46 to drive the motor 18. For example, by selectively enabling and disabling the FETs of the power switch network 46, the power received from the battery pack 22 is selectively applied to the stator windings of the motor 18 in a cyclic manner to cause the rotor of the motor 18 to rotate.

[0035] In some embodiments, the motor 18 is a sensorless motor that does not include a Hall effect sensor. Removing the Hall effect sensor provides the advantage of further reducing the size of the motor package. In these embodiments, the rotor position is detected based on detecting the current, back electromotive force (EMF), etc. in the inactive phase of the motor 18. Specifically, a current sensor, a voltage sensor, etc. are provided instead of a Hall sensor outside the motor 18, such as in the power switch network 46 or on the current path between the power switch network 46 and the motor 18. When the rotor 142 moves through the stator phase coils, the permanent magnets of the rotor 142 generate back EMF in the inactive phase. The electronic processor 42 detects the back EMF (e.g., using a voltage sensor) or the corresponding current (e.g., using a current sensor) generated in the inactive phase to determine the position of the rotor 142. The motor 18 is then commutated similarly as described above based on the position information of the rotor 142.

[0036] The electronic processor 42 uses the motor feedback information to ensure proper timing of the control signals to the power switch network 46 and to provide closed-loop feedback to control the speed of the motor 18 at a desired level. Specifically, the electronic processor 42 increases and decreases the duty cycle of the PWM signal provided to the power switch network 46 to maintain the speed of the motor 18 at the speed selected by the trigger 30. For example, as the load on the motor 18 increases, the speed of the motor 18 may decrease. The electronic processor 42 detects the decrease in speed using the rotor position sensor 134 or the back EMF sensor and proportionally increases the duty cycle of the PWM signal provided to the power switch network 46 (and thereby increases the electrical power provided to the motor 18) to increase the speed back to the selected speed. Similarly, when the load on the motor 18 decreases, the speed of the motor 18 may increase. The electronic processor 42 detects the increase in speed using the rotor position sensor 134 or the back EMF sensor and proportionally decreases the duty cycle of the PWM signal provided to the power switch network 46 (and thereby decreases the electrical power provided to the motor 18) to decrease the speed back to the selected speed. This operation of the electronic processor 42 may be continuous while the concrete vibrator 10 is operating.

[0037] In open loop speed control, electronic processor 42 maintains a constant duty cycle of the PWM signal (and thereby maintains constant electrical power provided to motor 18) corresponding to the position of trigger 30.

[0038] The electronic processor 42 is operable to receive the sensed position of the rotor 142 and commutate the electric motor 18 according to the sensed position. Additionally or alternatively, the electronic processor 42 is operable to receive the sensed speed of the rotor 142 and adjust the amount of power provided to the electric motor 18 in the above-described manner so that the motor 18 is driven at a desired speed. In the illustrated embodiment, the desired speed is a speed above 9,000 rpm. For example, the desired speed may be 10,000 rpm. Since the speed of the electric motor 18 is maintained at the desired speed, the vibration frequency of the vibrator head 28 is also maintained.

[0039] It is desirable to maintain the vibration frequency of the vibrator head 28 during operation of the concrete vibrator 10. When advancing the vibrator head 28 through wet concrete, it is important to vibrate the vibrator head 28 at a speed high enough for proper consolidation of the concrete. If the speed of the motor 18 drops below a threshold value, such as 9,000 rpm, the concrete will not consolidate properly. Additionally, if the speed of the motor 18 rises above a threshold value, such as 15,000 rpm, the concrete will not consolidate properly. Thus, if the vibration frequency falls outside of the threshold range, the integrity and appearance of the vibrated concrete will be negatively affected.

[0040] By sensing the speed of the rotor 142 and commutating the electric motor 18 based on the sensed speed, the motor 18 can avoid any speed differences due to changes in the state of charge of the battery pack 22. As the concrete vibrator 10 is used, the state of charge of the battery pack 22 is gradually depleted. The electronic processor 42 is operable to receive the sensed speed of the rotor 142 from the rotor position sensor 134 or the back EMF sensor and operate the commutation of the motor 18 independently of the state of charge of the battery pack 22.

[0041] By utilizing the electronic processor 42 and rotor position sensor 134 of the BLDC motor 18, the concrete vibrator 10 has many other advantages over other known pencil vibrators 10. First, the concrete vibrator 10 is able to operate at a higher efficiency than known pencil vibrators. By commutating the motor 18 based on the sensed rotor 142 speed, mechanical resistance and friction between components are eliminated. By commutating the motor 18 based on the sensed rotor 142 position, a constant phase advance can be optimized so that the load of the tool is relatively consistent. This is not achievable with a brushed DC electric motor. In a brushed DC electric motor, the brushes wear and the phase advance varies with the brush geometry. In this way, because the brushless DC motor 18 phase advance is optimized and does not change throughout use, high efficiency is maintained.

[0042] Second, electromagnetic compatibility (EMC) is reduced by eliminating EMC caused by brush / bar interaction in conventional motors. This could otherwise have a significant impact on the concrete vibrator 10 because the flexible shaft 26 and vibrator head 28 could act as antennas that receive undesirable EMC signals.

[0043] Fig. 9 A concrete vibrator 10 is illustrated that includes another embodiment of a whip assembly 200. The whip assembly 200 is coupled to the motor 18 and the vibrating head 28. The whip assembly 200 includes the shaft 26 and the sheath 27 as previously described. In this embodiment, the shaft 26 is a flexible shaft operable to transfer torque from the motor 18 to the vibrating head 28. The sheath 27 surrounds the shaft 26 and can prevent damage to the shaft 26.

[0044] like Fig. 9, the whip assembly 200 is provided with a bushing 204 at an intermediate position along the shaft 26, centered between the motor housing portion 14a and the vibrator head 28. The bushing 204 may be located between the motor housing portion 14a and the vibrator head 28 in other ways. The bushing 204 contacts both the shaft 26 and the sleeve 27 and supports the shaft 26 within the sleeve 27. The bushing 204 is positioned radially within the interior of the sleeve 27 and radially adjacent to the exterior of the shaft 26. In some embodiments, the bushing 204 may be a one-piece component. In other embodiments, the bushing 204 may be a multi-piece component, such as but not limited to a ball bearing. There is a nominal radial clearance between the bushing 204 and the shaft 26, thereby supporting the middle portion of the shaft 26 to rotate the shaft within the sleeve 27, while also preventing the shaft 26 from deflecting relative to the sleeve 27 in the radial direction. The bushing 204 may also suppress irregular vibrations of the shaft 26 within the sleeve 27 by controlling the modal vibration shape of the flexible shaft 26. In some embodiments, bushing 204 is a means of inhibiting deflection of flexible shaft 26 within sheath 27. In some embodiments, bushing 204 is also a means of supporting shaft 26 within sheath 27.

[0045] Fig.10 There is illustrated a concrete vibrator 10 that includes another embodiment of a whip assembly 300. The whip assembly 300 includes a flexible shaft 326 and a sheath 27 as previously described.

[0046] With Fig. 9Unlike the whip assembly 200 of FIG. 3 , which uses a bushing to reduce the radial clearance between the shaft 26 and the sheath 27, the flexible shaft 26 in the whip assembly 300 includes a stepped diameter portion 304 to reduce the radial clearance between the shaft 326 and the sheath 27. Similar to the bushing 204, the stepped diameter portion 304 is located at an intermediate position along the shaft 326, centered between the motor housing portion 14a and the vibrator head 28. The stepped diameter portion 304 can be located between the motor housing portion 14a and the vibrator head 28 in other ways along the shaft 326. A majority (i.e., greater than 50%) of the shaft 326 has an outer diameter D1 that nominally corresponds to the inner diameter of the sheath 27. The outer diameter D1 of the shaft 326 is slightly smaller than the inner diameter of the sheath 27 (i.e., the outer diameter D1 of the shaft 326 is nominally smaller than the inner diameter of the sheath 27), so that a radial clearance exists between the outer diameter of the shaft 326 and the inner diameter of the sheath 27. Thus, a running clearance is provided between the outer diameter D1 of the shaft 326 and the inner diameter of the sheath 27. In the illustrated embodiment, the stepped diameter portion 304 is disposed along a small portion of the shaft 26 such that the shaft 26 includes a modified outer diameter D2 that is nominally smaller than the inner diameter of the sheath 27. In the illustrated embodiment, the modified outer diameter D2 is greater than the outer diameter D1 of the remainder of the shaft 326. The sheath 27 further includes an outer diameter D3. In the illustrated embodiment, the outer diameter D3 of the sheath 27 does not change at a position radially adjacent to the stepped diameter portion 304. In other embodiments, the outer diameter D3 of the sheath 27 adjacent to the stepped diameter portion 304 may increase. With respect to the diameters D1, D2, and D3, these measurements are exemplary and do not require that the shaft 26 or the sheath 27 be cylindrical. In other words, the diameters D1, D2, and D3 may be the dimensions of the shaft 26 and / or the sheath 27 alone. The stepped diameter portion 304 can inhibit the shaft 326 from chasing between the motor housing portion 14a and the vibrator head 28 in the axial direction in a certain direction within the sheath 27. In some embodiments, the stepped diameter portion 304 is a device for inhibiting the flexible shaft 326 from deflecting within the sheath 27. In some embodiments, the stepped diameter portion 304 is also a device for supporting the flexible shaft 326 within the sheath 27.

[0047] Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention described.

[0048] Various features and advantages of the invention are set forth in the following claims.

Claims

1. A concrete vibrator, characterized in that: include: a housing having a motor housing portion extending along a longitudinal axis and a handle portion extending transverse to the longitudinal axis and spaced apart from the motor housing portion so as to define an opening between the handle portion and the motor housing portion; a trigger positioned within the opening, rearwardly of the motor housing portion, and extending from the handle portion of the housing; a brushless DC electric motor positioned within the motor housing portion; a battery pack configured to provide electric power to the electric motor to drive the motor; an electronic processor electrically connected to the motor and the battery pack, the electronic processor configured to regulate the electrical power supplied to the motor in a closed loop to maintain the motor operating at a speed set point; as well as A vibrator head is configured to receive torque from the motor to cause the vibrator head to vibrate.

2. The concrete vibrator according to claim 1, wherein: The trigger is configured as a variable speed trigger for outputting an electrical signal proportional to the degree to which the trigger is pressed to the electronic processor to change the rotation speed of the motor.

3. The concrete vibrator according to claim 1, wherein: The trigger is movable between at least two discrete trigger positions consistent with different rotational speeds of the motor.

4. The concrete vibrator according to claim 3, wherein: The trigger is movable between a first operating position in which the motor is driven at a first non-zero desired speed and a second operating position in which the motor is driven at a second non-zero desired speed different from the first non-zero desired speed.

5. The concrete vibrator according to claim 1, wherein: Further included is a flexible shaft having a first end coupled to the motor and an opposite second end coupled to the vibrator head, wherein the flexible shaft is configured to transfer torque from the motor to the vibrator head.

6. The concrete vibrator according to claim 1, wherein: Further included is a power switch network including a plurality of field effect transistors selectively activated by the electronic processor to control the motor to operate at the speed set point.

7. The concrete vibrator according to claim 6, wherein: The power switch network includes six field effect transistors that receive pulse width modulated signals from the electronic processor to selectively apply power to the motor to maintain the motor at the speed set point.

8. The concrete vibrator according to claim 1, wherein: Further included is a rotor position sensor coupled to the electronic processor, wherein the rotor position sensor is configured to output a signal indicative of at least one of a position, a speed, or an acceleration of the motor to the electronic processor.

9. The concrete vibrator according to claim 8, wherein: The rotor position sensor is a Hall effect sensor.

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