GB2381566A

GB2381566A - Adjusting eccentric weight vibrator

Info

Publication number: GB2381566A
Application number: GB0218094A
Authority: GB
Inventors: Dean R Potts
Original assignee: Caterpillar Paving Products Inc
Current assignee: Caterpillar Paving Products Inc
Priority date: 2001-10-31
Filing date: 2002-08-05
Publication date: 2003-05-07
Also published as: GB0218094D0; US20030082001A1

Abstract

A vibratory mechanism 26 for a compactor (Fig 1) with a vibrating drum (14,16) comprises a first eccentric weight 50 on a shaft 54, 58, 72, a second eccentric weight 52 on a shaft 56, 60, 76 and a clutch 70 interconnecting the shafts and allowing relative rotation of the weights to vary the vibration amplitude of the mechanism. The inner weight 50 is directly driven from motor 28 via inner shaft 54, inner drive shaft 58 and shaft 72. The outer weight 52 is supported on a stub shaft 56 and driven along with the inner weight via an outer drive shaft 60, a shaft 76 and a clutch 70 with a clutch pack 78. The clutch 70 may be an electric, hydraulic or spring-actuated disc clutch. As the motor 28 is brought up to speed, the clutch 70 is activated momentarily to allow the shafts 72, 76 to slip relative to each other until the weights 50, 52 are positioned 180 deg out of phase giving a vibration amplitude of zero. The clutch is then re-engaged and the shafts 72, 76 brought up to speed. The clutch is then activated again to allow the weights to move towards each other to increase the vibration amplitude to a desired level. The clutch activation is automatically controlled (controller 100, Fig 4).

Description

VARIABLE VIBRATORY MECHANISM

Technical Field

5 This invention relates generally to a vibratory compactor machines and, more particularly, to an infinitely variable amplitude and frequency vibratory mechanism.

Background

Vibratory compactor machines are commonly employed for 10 compacting freshly laid asphalt, soil, and other compactable materials. For example these compactor machines may include plate type compactors or rotating drum compactors with one or more drums. The drum type compactor functions to compact the material over which the machine is driven. In order to compact the material the drum assembly includes a vibratory mechanism 15 including inner and outer eccentric weights arranged on a rotatable shaft within the interior cavity of the drum, for inducing vibrations on the drum.

The amplitude and frequency of the vibratory forces determine the degree of compaction of the material, and the speed and efficiency of the compaction process. The amplitude of the vibration forces is changed by 2 0 altering the position of a pair of weights with respect to each other. The frequency of the vibration forces is managed by controlling the speed of a drive motor in the compactor drum.

The required amplitude of the vibration force may vary depending on the characteristics of the material being compacted. For 2 5 instance, high amplitude works best on thick lifts or harsh mixes, while low amplitude works best on thin lifts and soft materials. Amplitude variation is important because different materials require different levels of compaction.

Moreover, a single compacting process may require different amplitude levels

because higher amplitude may be required at the beginning of the process, and the amplitude may be gradually lowered as the process is completed.

Conventional vibratory compactor machines are problematic in that the amplitude and frequency of the vibration force can only be set to 5 certain predetermined levels, or the mechanisms for adjusting the vibration amplitude are complex. One such vibratory mechanism is disclosed in U.S. Patent No. 4,350,460 issued to Lynn A. Schmelzer et al. on 21 September 1982 and assigned to the Hyster Company.

The present invention is directed to overcome one or more of 10 the problems as set forth above.

SummarY of the Invention

According to one aspect of the invention, a vibratory mechanism comprises a motor and a clutch having first and second output shafts. The clutch is connected to the motor. A first eccentric weight is 15 connected to the first output shaft of the clutch and a second eccentric weight is connected to the second output shaft of the clutch. The clutch is operative to engage and disengage the first and second output shafts Tom each other to change a phase difference between the first and second eccentric weights.

According to another aspect of the invention, a method is 2 0 provided for ad lusting amplitude of a vibratory mechanism, the vibratory mechanism including first and second eccentric weights, a motor for driving the first and second eccentric weights, and a clutch connected to the motor and having first and second output shafts connected to the first and second eccentric weights, respectively, comprising: 2 5 activating the clutch to change a phase difference between the first and second eccentric weights in order to change the vibration amplitude.

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Brief Description of the Drawings

The invention will be more fully understood from the following detailed description of the preferred embodiment, taken in

connection with the accompanying drawings, in which: 5 Fig. 1 is a side elevational view of a work machine embodying the present invention; Fig. 2 shows an axial cross section view talcen along line 2-2 through a compacting drum of the work machine of Fig. 1 embodying the present invention; 10 FIG. 3 is an enlarged sectional view of FIG. 2; FIG. 4 is a system diagram; FIG. 5 is a flow chart showing an operation mode of the vibratory compactor machine; and FIGS. 6A and 6B illustrate an example of alignment index 15 points for a rotation sensing device being unaligned and aligned, respectively.

Detailed Description

A work machine 1 O. for increasing the density of a compactable material 12 or mat such as soil, gravel, or bituminous mixtures, an example of which is shown in Fig. 1. The work machine 10 is for 2 O example' a double drum vibratory compactor, having a first compacting drum 14 and a second compacting drum 16 rotatably mounted on a main frame 18.

The main frame 18 also supports an engine 20 that has a first and a second power source 22,24 conventionally connected thereto. Variable displacement fluid pumps or electrical generators can be used as interchangeable 2 5 alternatives for the first and second power sources 22,24 without departing from the present invention.

The first compacting drum 14 includes a first vibratory mechanism 26 that is operatively connected to a first motor 28. The second compacting drum 16 includes a second vibratory mechanism 30 that is 3 O operatively connected to a second motor 32. The first and second motors 28,32 are operatively connected, as by fluid conduits and control valves or

electrical conductors and controls to the first power source 22. It should be understood that the first and second compacting drums 14,16 could have more than one vibratory mechanism per drum.

In as much as the first compacting drum 14 and the second 5 compacting drum 16 are structurally and operatively similar, the description,

construction and elements comprising the first compacting drum 14, which will now be discussed in detail and as shown in Fig. 2, apply equally to the second compacting drum 16. Rubber mounts 36 vibrationally isolate the compacting drum 14 from the main frame 18. The first compacting drum 14 1 0 includes a propel motor 40 that is connected to the second power source 24.

For example, the propel motor 40 is connected to the main fraTne 18 and operatively connected to the first compacting drum 14 in a known manner.

The second power source 24 supplies a pressurized operation fluid or electrical current, to propel motor 40 for propelling the work machine 10.

1 5 Still referring to Fig.2, the vibratory mechanism 26 is contained within a housing 46 that is coaxially supported within the first compacting drum 14 in a known manner. The vibratory mechanism 26 includes a f rstlinner eccentric weight 50 and a second/outer eccentric weight 52. An inner shaft 54 supports the inner eccentric weight 50 and a pair of stub 2 0 shafts 56 supports the outer eccentric weight 52. Motor 28 is connected to inner and outer drive shafts 58,60. Inner drive shaft 58 is connected to the inner shaft 54 and outer drive shaft 64} is connected to the one of the stub shafts 56. The inner drive shaft 58 is shown as being a conventional cardan type drive shaft with universal joints and outer drive shaft 60 is shown as 2 5 being a hollow tube type shaft with a rubber, tire-type flexible drive coupling 62 at each end that allows flexibility and misalignTnent capabilities equal to the inner drive shaft 58. The flexible drive couplings 62 are of the split type so that the outer drive shaft 60 can be disassembled without removing the drum 14 from the work machine 10. With this structure, the drive shafts 30 58,60 are concentrically arranged.

Motor 28 supplies rotational power to the inner and outer eccentric weights 50,52 so as to impart a vibratory force on compacting drum __,. . _,... _,, i__ _ I_ BIneI! -! I! I!! !! I_! _!!! B! _ I-_

14. A clutch 70 is connected to motor 28. Clutch 70 has dual concentric output shafts with an inner output shaft 72 connected to an output shaft 74 of the motor 28 and an outer output shaft 76 of the clutch 70 connected to the inner output shaft 72 of the clutch 70 via a clutch pack 78 (e.g., a disk clutch 5 or similar clutch). The clutch 70 may be either electric, hydraulic, or spring actuated. For purposes of discussion, it will be assumed that the outer output shaft 76 is releasably connected to the output shaft 74 of the motor 28 although the clutch 70 could easily be configured in an alternate way.

In the embodiment illustrated in Fig. 3, a hydraulic piston 80 is 1 0 provided in the clutch 70 for engaging or disengaging the clutch 70, thereby providing for the outer output shaft 76 to slip relative to the inner output shaft 72. A rotation sensing device 82 (see Fig. 4) is provided at each of the output shafts 72,76 of the clutch 70 for detecting the speed and position of 1 5 the first and second eccentric weights 50,52. In particular, a speed sensor port 84, 86 is disposed at an outer portion of each of the inner and outer output shafts 72 (see Fig. 3), for sensing the speed and positions of the weight driveshafts 58,60 and thus, the first and second eccentric weights 50,52. Each output shaft 72,76 has a unique profile at one point of rotation called an index 2 0 point. For example, a gear tooth type target 90 for a proximity switch sensor 92 has a tooth missing at one point (index point). With this configuration, both the speed and position of the shaft can be determined with appropriate electronic sensing hardware. Specifically, the index point is matched to the position of the corresponding eccentric weights. If an index point of the 2 5 switch sensor 92 is aligned with the index point of the gear tooth type target 90, the inner and outer eccentric weights 50,52 are aligned; on the other hand, if the index points are 180 apart, then the weights 50,52 are directly opposite each other.

With reference to the illustrated system schematic of FIG. 4, a 3 0 computer controller 100 may be connected to the rotation sensing device 82 to monitor the positions of the output shafts 72,76. The computer controller 100 controls the displacement of the power source 22 in response to operator input

and preprogrammed control algorithms in order to adjust the vibration amplitude and speed. In particular, the controller 100 is connected to a valve, or electrical switch for causing the clutch 70 to engage and release, thereby changing the phase difference between the first and second eccentric weights 5 50,52.

The computer controller 100 is connected to an operator interface 102. Operator interface 102 is defined as being any known device or combination of input devices such as touch screens, levers, rotary knobs, push buttons, joysticks and the like. Operator interface 102 and the controller 100 1 0 are connected to the first and second power sources 22, 24, motors 28,40, rotation sensing device 82 and one or more accelerometers 104.

The controller 100 can monitor drum acceleration via the accelerometers 104 mounted on a frame 18 and vibrator speed via one or more sensors 92 sensing the output shafts 72,76 and control the output from 1 5 the power sources 22,24 per a preprogrammed decision algorithm. The operator inputs commands from the operator interface 102 to the controller 100 when vibration is needed and the controller 100 would respond with the appropriate signal command to the power source 22.

Industrial Applicability

2 0 During use of the work machine 10, an operator requests propel from power source 24 so that the drum 14,16 rotates around in a desired direction. Rotating the drum 14,16 in this manner causes the work machine 10 to move over the compactable material 12.

In operation before actually driving the work machine 10 onto 2 5 the mat 12 to be compacted, the operator requests vibration from the operator interface 102 to actuate motor 28. This causes the controller 100 to command the inner and outer weight driveshafts 58,60, along with the inner and outer eccentric weights 50,52, to rotate.

The position of the inner and outer eccentric weights 50,52, 3 0 with respect to each other, determines the amplitude of the vibrational force imparted on the drum 14,16. For instance, if the inner and outer eccentric , it _ _.__,,,,.,.,,,,.,,,,,,.,_.,. _, il _ rl _ _ Ia I

weights 50,52 are positioned 180 from each other, their weights counteract and zero amplitude is obtained. If the inner and outer eccentric weights 50,52 are positioned 0 from each other, a maximum amplitude is obtained.

The operator interface 102 may include a switch having three 5 positions: (1) everything off; (2) vibrator drive motor running but zero amplitude; and (3) vibrator motor running and amplitude and frequency under computer control. A fourth position can be provided which turns over the speed and amplitude control to the operator.

The controller 100 causes the power source 22 to gradually 1 0 increase output so as to bring the motor 28 up to speed. As the speed of the motor 28 increases, the controller 100 monitors the speed and position of the inner and outer weight driveshafts 58,60 and activates the clutch 70 momentarily to allow the output shafts 72,76 to slip relative to each other until the 180-degree out of phase position is reached. This ensures that the 1 5 vibratory mechanism 26 can come up to speed without passing through a resonant phase and causing unnecessary wear and tear to the rest of the work machine 10. Once the out of phase (substantially zero amplitude) position is reached, the clutch 70 remains engaged and the controller 100 quickly brings motor 28 up to a desired speed.

2 0 When the output shafts 72,76 have reached the desired speed, the controller 100 activates the clutch 70 again to cause the outer output shaft 76 to slip relative the inner output shaft 72 to increase the amplitude to a desired level.

In particular, the controller 100 controls the clutch 70 to either 2 5 engage or release, so as to fix output shafts 72,76 in their desired phased position. The clutch 70 causes the outer output shaft 76 to slip relative to the inner input shaft 72, thus, causing the outer eccentric weight 52 to rotate with respect to the inner eccentric weight 52. As the inner and outer eccentric weights 50,52 rotate with respect to each other, the phase relationship there 3 0 between is altered, and thus, the vibration amplitude is changed. Since the relative positions of the inner and outer eccentric weights 50,52 are not J

stepped or incremental, continuously variable adjustments can be made to the amplitude. At the highest amplitude, normally used during the first passes, the RPM of the shafts may be reduced to keep bearing loads within their 5 design limits. The controller 100 may slow the speed of motors 28, 32 to accomplish this feature.

During the compaction process, the energy absorbed by the drum 14,16 tends to cause the outer weight driveshaft 60 to slow down. Thus, the controller continuously monitors the shaft positions and does not allow the 10 clutch 70 to disengage again once the desired amplitude is reached. Also, as the surface being compacted becomes denser, the drum may de- couple from the compactable material 12. The controller 100 senses this phenomenon via the accelerometers 104 and commands the clutch 70 to disengage in order to change the amplitude and increases the output of the motor 28 to increase the 15 speed/frequency of the vibratory mechanism 26,30. Known control theories and hardware have been developed by companies, such as Geodynamik, to provide a compaction indicator combined with a compactor control system to achieve this function.

At the end of each pass, the controller 100 actuates the clutch 2 0 70 to return the outer weight 52 to be 180 out of phase with the inner weight SO to achieve a zero (or substantially zero) amplitude setting. As conditions change, i.e., the material becomes more dense, a different amplitude may be desired. In this case, the different amplitude can be selected either automatically by the controller labor via an operator input, wherein the 2 5 controller again allows the outer output shaft 76 to slow down until the proper phase is detected and then the output shafts are again locked together.

With the manual operator control, the operator interface 102 may include a three-position switch provided for the amplitude settings. The threepositions may include: (1) everything off, no shafts turning; (2) vibrator 3 0 running at speed but at zero amplitude; and (3) vibrator running at speed and at maximum amplitude permissible for the conditions.

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In a modified embodiment, the clutching function could be accomplished using a series of very short (milliseconds) command signals to the clutch 70 disengage. This modified embodiment may be useful with small work machines using an electric slip clutch wherein two shafts extend from 5 the clutch. Using pulse width modulation, a good release function is possibly with only a little pulse function.

Shown and described are several preferred embodiments of the invention, though it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention 10 in its broader aspects. Therefore it is intended that the appended claims cover all such changes and modifications as fall within the scope of the invention.

Claims

-10 Claims

1. A vibratory mechanism (26), comprising: a motor (28), 5 a clutch (70) having first and second output shafts (72 76), said clutch (70) being connected to said motor (70); a first eccentric weight (50) connected to the first output shaft (72) of said clutch (70); a second eccentric weight (52) connected to the second output 1 0 shaft (76) of said clutch (70); and wherein said clutch (70) is operative to engage and disengage said first and second output shafts (72,76) from each other to change a phase difference between said first and second eccentric weights (50,52).

2. The vibratory mechanism (26) of claim 1, wherein said clutch 1 5 (70) includes a hydraulic piston (80) for engaging and disengaging said first and second output shafts (72,76) of said clutch (70).

3. The vibratory mechanism (26) of claim 1 or 2, including an inner drive shaft (58) connected between said first output shaft (72) and said first eccentric weight (50) and an outer drive shaft (60) connected between said outer 2 0 drive shaft (76) and said outer eccentric weight (52).

4. The vibratory mechanism (26) of any preceding claim, further including a controller (100) for controlling said clutch (70) based on detected operating conditions.

5. The vibratory mechanism (26) of claim 4, further including a rotation sensing device (82) for detecting a position of each of said first and second eccentric weights (50,52).

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6. The vibratory mechanism (26) of claim 4 or 5, wherein the detected operating conditions correspond to the position detected by said rotation sensing device (82).

7. The vibratory mechanism (26) of claim 4 or 5, wherein the detected operating conditions correspond to conditions detected by an accelerometer (104).

8. The vibratory mechanism (26) of any preceding claim, 10 including means for detection compaction of a material (12) being compacted by the vibratory mechanism (26).

9. The vibratory mechanism (26) of any of claims 4 to 7 wherein said controller ( 100) is operative to be controlled by manual operation of at least 15 three positions of vibration amplitude settings.

10. A work machine (10), comprising: a compacting drum (14) supporting said work machine (lO); and a vibratory mechanism (26) as set forth in any of claims 1 to 9.

2 0

1 1. A method for adjusting amplitude of a vibratory mechanism (26), the vibratory mechanism (26) including first and second eccentric weights (50,52), a motor (28) for driving the first and second eccentric weights (50,52), and a clutch (70) connected to the motor (28) and having first and second output shafts (72,76) connected to the first and second eccentric weights (50,52), 25 respectively, comprising: activating the clutch (70) to change a phase difference between the first and second eccentric weights (50,52) in order to change the vibration amplitude.

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12 12. The method according to claim 11, wherein said activating step includes disengaging a one of the first and second output shafts (72,76) from another one of the first and second output shafts (72,76) so that the one of the first and second output shafts (72,76) slips relative to the other one of the first 5 and second output shafts (72,76), thereby changing the phase difference of the first and second eccentric weights (50,52).

13. The method according to claim 12, wherein said disengaging step includes momentarily actuating a hydraulic piston (80) for disengaging the one of the first and second output shafts (72,76) from the other one of the first 1 0 and second output shafts (72,76).

14. A method for adjusting amplitude of a vibratory mechanism (26) as it makes a plurality of passes over a compactable material (12), the vibratory mechanism (26) including first and second eccentric weights (50, 52), a motor (28) for driving the first and second eccentric weights (50, 52), and a clutch

1 5 (70) connected to the motor (28) and having first and second output shaRs (72,76) connected to the first and second eccentric weights 50,52, respectively, comprising: monitoring a speed and position of the output shafts (72,76) via a computer controller (100); 2 0 engaging or disengaging the clutch (70) to cause the first and second eccentric weights (50,52) to be 180 out of phase; and engaging or disengaging the clutch (70) to increase the vibration amplitude to a desired level after a desired RPM is reached.

2 5 15. The method according to claim 14, further comprising: monitoring the vibration speed and amplitude via the controller (100); and controlling the clutch (70) to decrease the vibration amplitude to substantially zero at the end of each pass.

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-13-

16. A vibratory mechanism as hereinbefore described with reference to the accompanying drawings.

17. A work machine as hereinbefore described with reference to 5 the accompanying drawings.

18. A method for adjusting amplitude of a vibratory mechanism as hereinbefore described with reference to the accompanying drawings.