GB2381565A

GB2381565A - Adjusting eccentric weight vibrator

Info

Publication number: GB2381565A
Application number: GB0218085A
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: US20030082002A1; GB0218085D0

Abstract

A vibratory mechanism 26 for a compactor (Fig 1) with a vibrating drum 14,16 comprises a first eccentric weight 50, a second coaxially rotatable eccentric weight 52 and a clutch 60 between them, the clutch allowing relative rotation of the weights to vary the vibration amplitude of the mechanism. The outer weight 52 is directly driven from motor 28 via shaft 58 and stub shafts 56. The inner weight 50 is supported on an inner shaft 54 and driven along with the outer weight via a clutch 60 disposed between the shafts 54 and 56. The clutch 60 is a torque limiting slip clutch of the ball ramp type as shown, or jaw type with spring tension or friction disc type. With the vibratory mechanism at rest, the weights are positioned 180 deg out of phase so the amplitude is zero. The motor accelerates the weights up to speed slowly so that the slip clutch does not activate and the amplitude does not change. At a certain speed, the motor 28 abruptly changes speed, the clutch 60 slips, and the weights move towards each other to increase the vibration amplitude. The power applied to the motor 28 is automatically controlled (controller 80, Fig 4).

Description

VARIABLE VIBRATORY MECHANISM

Technical Field

This invention relates generally to a vibratory compactor machines 10 and, more particularly, to an infinitely variable amplitude and frequency vibratory mechanism.

Background

Vibratory compactor machines are commonly employed for compacting freshly laid asphalt, soil, and other compactable materials. For 15 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 including inner and outer eccentric weights arranged on a rotatable shaft within 2 0 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 altering the position of a pair of weights with respect to each other. The frequency of the 2 5 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 instance, high

- 2 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 5 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 certain predetermined levels, or the mechanisms for adjusting the vibration amplitude are 10 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 the problems as set forth above.

15 Summary of the Invention

In one aspect of the invention, a vibratory mechanism is provided that includes an inner eccentric weight rotatably supported within a housing. An outer eccentric weight is rotatably supported and positioned about the inner eccentric weight. A clutch operatively connects the inner and outer eccentric 2 0 weights.

According to another aspect of the invention, a method for controlling a vibration amplitude of a vibratory compactor includes abruptly changing a speed of one of an inner and outer eccentric weights to cause a clutch to slip, thereby causing inner and outer eccentric weights to move farther apart or 2 5 closer together to change the vibration amplitude.

Brief Description of the Drawings

Fig. 1 is a side elevational view of a work machine embodying the present invention; .,_ - _e At_ I- 1 1 1 if 11 11 111815 111_11: 1 1:1 11 1 1 1111 11 1 1

Fig. 2 shows an axial cross section view taken along line 2-2 through a compacting drum of the work machine of Fig. I embodying the present invention; FIG. 3 is an enlarged sectional view of the vibrator pod shown in 5 FIG. 2; and FIG. 4 is a system diagram.

Detailed Descrintion A work machine 10, for increasing the density of a compactable material 12 or mat such as soil, gravel, or bituminous mixtures, an example of 10 which is shown in Fig. 1. The work machine lO is for 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 15 electrical generators can be used as interchangeable 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 operatively connected to a 2 0 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. 2 5 In as much as the first compacting drum 14 and the second 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 30 drum 14 from the main frame 18. The first compacting drum 14 includes a

- 4 - propel motor 40 that is connected to the second power source 24. For example, the propel motor 40 is connected to the main frame 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 5 propelling the work machine 10.

Referring now to Fig.2, the vibratory mechanism 26 is contained within a housing 46 that is coaxially supported within the first compacting drum 26 in a known manner. The vibratory mechanism 26 includes a f rst/inner eccentric weight 50 and a second/outer eccentric weight 52. An inner shaft 54 10 supports the inner eccentric weight and a pair of stub shafts 56 supports the outer eccentric weight 52. Motor 28 is connected to a drive shaft 58 that is connected to one of the stub shafts 56 to supply rotational power to the vibratory mechanism 26 so as to impart a vibratory force on compacting drum 14.

The outer eccentric weight 52 is mechanically coupled to shaft 54 15 so that it is directly rotated by the vibrator propel motor 28. The inner eccentric weight 50 is rotatably mounted concentrically with respect to the outer eccentric weight 52, and is driven along with the outer eccentric weight 52, via a torque limiting (slip) clutch 60 (see Figs.2 and 3) disposed between the inner shaft 54 and one of the stub shafts 56. Clutch 60 may be internal to the vibratory 20 mechanism 26, as shown in Fig.3 or external. The clutch 60 may be of a variety of types, such as but not limited to' a jaw type with spring tension, a ball ramp (such as shown in Figs.2 and 3), and a friction disk type. As shown in Fig. 3, the clutch 60 may be provided with a torque adjustment screw 62 and tension spring 64 for adjusting a clutch force.

2 5 As shown in Fig.3, the inner weight drive shaft 50 is supported by bushings 70 within the stub shafts 56. In addition, the stub shafts 56 are supported by bearings 72 within the housing 46 of the vibratory mechanism 26.

Optionally, vibratory mechanism 26 may be modified to limit the rotation of the inner eccentric weight 50 within the outer eccentric weight 52 to 3 0 180 degrees with an internal stop mechanism, such as for example rubber covered stop pins 74 bolted through the stub shafts 56. Inner eccentric weight 50 contacts I. 1 1. 1:_ 1 8 11111_111 11511111,.11 111111811_11 1 111111 1

the stop pins 74 at two different positions. This insures a positive location of the minimum amplitude (could be zero, e.g., when the weights are 180 degrees apart) and the maximum amplitude (e.g., when the weights are O degrees apart) settings.

The stop pins 74 are useful to simplify the control of the vibratory mechanism 26.

5 Typically, as shown in Fig. 4, a controller 80 is positioned on the work machine 10. Controller 80 receives input commands from an operator interface 120 and sends output commands to the first and second power sources 22, 24 for operating the vibrator motor 28 and propel motor 40 respectively. The operator interface 120 is defined as being any known device or combination of 10 input devices such as touch screens, levers, rotary knobs, push buttons, joysticks and the like. The second power source 24 drives the propel motor 40, and is also controlled by the operator interface 120 and/or by controller 80.

The controller 80 can monitor drum acceleration via one or more accelerometers 84 mounted on a frame 18 and vibrator speed via one or more 15 speed sensors 86 on the drive shaft 56 and control the output from the power sources 22,24 per a preprogrammed decision algorithm (see Fig. S. for example).

The operator inputs commands from the operator interface 82 to the controller 80 when vibration is needed and the controller 80 would respond with the appropriate signal command to the power source 22.

2 0 Industrial ADPlicabilitv During operation of the work machine 10, an operator actuates the propel motor/motors 40 such that the drums 14,16 rotate around a central axis in the desired direction. Rotating the drums 14,16 in this manner causes the work machine 10 to move in forward or reverse over the material 12 to be compacted.

2 5 In addition, the operator actuates the motor/motors 28,32, which causes the drive shaft 58 (e.g., a cardan type flexible driveshaft shown in Fig. 2), along with the inner and outer eccentric weights 50,52, to rotate.

The position of the inner and outer eccentric weights 50,52, with respect to each other, determines the amplitude of the vibrations in the drum 3 0 member. For example, if the inner and outer eccentric weights 50,52 are

- 6 positioned 1800 from each other, their weights counteract and zero amplitude (or a minimum amplitude) is obtained. If the inner and outer eccentric weights 50,52 are positioned 00 from each other, their weights combine and maximum amplitude is obtained. The inner and outer eccentric weights 50,52 can be 5 positioned in an infinite number of positions, so that infinite vibration amplitude levels can be obtained.

During operation the vibratory mechanism 26 functions as follows: When the work machine to is started the vibratory mechanism 26 1 0 is at rest with the inner and outer eccentric weights 50,52 at 180 degrees out of phase, so that the net amplitude is minimal or at zero. The operator signals for vibration from the operator interface 82. The controller 80 then increases the output from the power source 22, increasing the power supplied to the motor 28 at a relatively slow rate of speed. (2-8 seconds) In turn, the motor 28 accelerates 15 the inner and outer eccentric weights 50,52 up to speed slowly enough that the slip clutch 60 does not activate (and therefore the amplitude does not change). At 90-100 % of desired speed (or at some speed faster than frame resonance), the power source 22 suddenly surges to full output for a short period of time (20 milliseconds to 0.5 seconds estimated), which causes the clutch 60 to slip and 2 0 increases the amplitude as the inner and outer eccentric weights 50,52 are moved out of 180 degree opposition. (Note: power source 22 output may be larger than what is required to drive the motor 28 at maximum frequency so that the amplitude adjustment can occur at a predetermined speed.) The controller 80 monitors the response in the vibration of the 2 5 drum 14 and may also determine the response of the material 12 being compacted via accelerometers 84 mounted on the drum 14 and frame 18. Conventional controllers 80 and other hardware (such as made by Geodynamik, for example) could be used for this application, which is in effect a compaction indicator combined with a compactor control system.

3 0 If the vibration sensed is not adequate for compaction, the amplitude is changed until the desired amplitude is reached. This is sensed by _e Be- an_ ll_ _ a_ Il 1 TI1_111; _ 111_1_ 1B 1

- 7 identifying the point (amplitude) at which de-coupling of the drum 14 from the surface of the material 12 being compacted occurs, and then backing off slightly.

The entire system can be monitored via the accelerometers 84 andior the speed sensors 86. Normally, the accelerometers 84 could be used to 5 determine the vibrator speed, but at low/no amplitude the speed sensors 86 may be needed.

Additionally, the computer controller 80 can monitor ground speed and based on input parameters, limit or control ground speed by controlling operation of power source 24 which drives the drive motor 40. This would be 10 useful to control impact spacing for producing pavements with superior ride characteristics or to manage the compaction process to optimize the productivity of the machine.

When the vibratory mechanism 26 is stopped suddenly, the slip clutch 60 operates and allows the inner and outer weights 5O,52 to rotate relative 15 to each other to be 180 degrees out of phase and at zero amplitude. Stop pins 74 could be provided to limit the rotation of the inner and outer weights 50,52 to 180 degrees total rotation in either direction. This concept would also work with weight shafts that had continuous rotation capability, using a slightly more complex control theory.

2 0 The entire concept can also work if the orientation of the weights is reversed. That is, the vibrator decreases amplitude with sudden increases in speed and increases amplitude with sudden decreases in speed. From one perspective, this might work better as the vibrator could be suddenly turned on and it would go to zero or very low amplitude and high RPM. As the RPM was 2 5 suddenly dropped, amplitude would increase and a new lower speed would be set at the same time. However, normally compaction could be expected to start at low RIM and high amplitude and increase RPM and decrease amplitude as the soil or asphalt mat was being compacted and got stiffer.

Shown and described are several embodiments of the invention, 3 0 though it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader

- 8 aspects. Therefore it is intended that the appended claims cover all such changes and modifications as fall within the scope of the invention.

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Claims

- 9 - Claims

1. A vibratory mechanism (26) comprising: a first eccentric weight (50) rotatably supported within a housing 5 46; a second eccentric weight (52) coaxially rotatable with said first eccentric weight (50); and a clutch (60) operatively connecting said first and second eccentric weights (50, 52), said clutch (60) being operative to index said first eccentric 10 weight (50) relative to said second eccentric weight (52) to change a vibration amplitude of the vibratory mechanism (26).

2. The vibratory mechanism (26) in claim 1, wherein said clutch (60) is a torque limiting clutch, interposed said first and second eccentric weights (50,52), that slips to allow relative movement between said first and second 15 eccentric weights (50,52).

3. The vibratory mechanism (26) in claim 1 or 2, wherein said clutch (60) is an adjustable clutch.

4. The vibratory mechanism (26) in any preceding claim, further including a motor (28) for driving said first and second eccentric weights (50,52).

S. The vibratory mechanism (26) in claim 4, including a shaft (58) connecting said motor to said first and second eccentric weights (50,52).

6. The vibratory mechanism (26) in claim 4 or 5, including a variable power source (22) connected with said motor (28).

2 5 7. The vibratory mechanism (26) in claim 6, wherein an operator interface (80) controls said power source (22).

8. A work machine (10), comprising:

- 1 0 a compacting drum (14) supporting said work machine (10), and a vibratory mechanism (26) as set forth in any of claims 1 to 7.

9. A method for controlling amplitude of a vibratory mechanism (26), the vibratory mechanism (26) having first and second eccentric weights 5 (50, 52) coaxially rotatably coupled by a torque limiting clutch (60) operatively connecting, comprising: abruptly changing a speed of one of the first and second eccentric weights (50,52) to cause the torque limiting clutch (60) to slip, thereby causing the first and second eccentric weights (50,52) to move farther apart or closer 10 together to change the vibration amplitude.

10. The method according to claim 9, including: determining at least an amount of vibration; and changing the vibration amplitude based on the detected vibration.

11. The method according to claim 9 or 10, including repeating 15 said speed changing step to arrive at a desired vibration amplitude.

12. The method according to any of claims 9 to 11, including monitoring a vibration frequency, and controlling the vibrator so that a desired area of vibration frequency versus vibration amplitude is maintained.

13. The method according to claim 12, wherein as the vibration 2 0 frequency is increased, the vibration amplitude is decreased, and wherein as the vibration frequency is decreased, the vibration amplitude is increased.

14. The method according to any of claims 9 to 13, including monitoring a ground speed of a vehicle that includes the vibratory compactor, and controlling the ground speed and the vibration amplitude relative to each other.

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

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-11 16. A work machine as hereinbefore described with reference to the accompanying drawings.

17. A method for adjusting amplitude of a vibratory mechanism 5 as hereinbefore described with reference to the accompanying drawings.