US3909147A

US3909147A - Variable amplitude vibration generator

Info

Publication number: US3909147A
Application number: US521754A
Authority: US
Inventors: Harry H Takata
Original assignee: Raygo Inc
Current assignee: Caterpillar Paving Products Inc
Priority date: 1974-11-07
Filing date: 1974-11-07
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30
Also published as: JPS5421019B2; JPS5158766A

Abstract

A variable amplitude vibration generator especially adapted for use with compacting machines in which a primary weight is eccentrically fixed to a power driven rotatably mounted shaft and a secondary weight eccentrically freely rotatably mounted on the shaft is releasably securable to the shaft by activating a remotely controllable detent connection, in an in-phase relationship with the primary weight to provide high amplitude vibration, and in which - upon rotation of the shaft in either direction though slightly less than 180* - with the detent connection deactivated, an out-of-phase relationship is established between the primary and secondary weights to provide for low amplitude vibration.

Description

United States Patent Takata 1 Sept. 30, 1975 [54] VARIABLE AMPLITUDE VIBRATION 3.797.954 3/1974 Harris 404/117 3,814,532 6/1974 Barrett 404/117 GENERATOR [75] Inventor: Harry H. Takata, Golden Valley,

Minn.

[73] Assignee: Raygo, Inc., Minneapolis Minn.

[22] Filed: Nov. 7, 1974 [21] Appl. No.: 521,754

[52] US. Cl. 404/117; 404/133 [51] Int. Cl. EOIC 19/38 [58] Field of Search 404/117, 133; 74/87 [56] References Cited UNITED STATES PATENTS 3,192,839 7/1965 Vivier .Q 404/117 3,598,029 8/1971 Paramythioti.. 404/1 17 3.605.584 9/1971 Kaltenegger 404/117 3,670,631 6/1972 Gaylord 404/117 3.722381 3/1973 Tuneblom 404/1 17 Primary Examiner-Nile C. Byers Jr.

[57] ABSTRACT A variable amplitude vibration generator especially adapted for use with compacting machines in which a primary weight is eccentrically fixed to a power driven rotatably mounted shaft and a secondary weight eccentrically freely rotatably mounted on the shaft is releasably securable to the shaft by activating a remotely controllable detent connection, in an in-phase relationship with the primary weight to provide high amplitude vibration, and in which upon rotation of the shaft in either direction though slightly less than 180 with the detent connection deactivated, an out-ofphase relationship is established between the primary and secondary weights to provide for low amplitude vibration.

21 Claims, 12 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of7 3,909,147

PIC-Q US. Patent Sept. 30,1975 Sheet 2 of7 3,909,147

U.S. Patsnt Sept 30,1975 Sheet 3 of7 $909,147

US. Patent Sept. 36,1975 Sheet 4 of7 3,909,147

US. Patent Sept. 30,1975 Sheet 7 of7 3,909,147

F'IGJO.

MEDIUM AMPLITUDE 29 154 2W ag/mg I VARIABLE AMPLITUDE VIBRATION GENERATOR This invention relates to vibration generators and refers more particularly to variable amplitude vibration generators especially adapted for use in compacting and surface finishing machines. Such machines, equipped with variable amplitude vibration generators of one form or another, have been available heretofore. The Barrett et al. U.S. Pat. No. 3,814,532 and the Tuneblom US. Pat. No. 3,722,381 illustrate examples of such prior vibration generators. Like the variable amplitude generators of these patents, the vibration generator of this invention employs primary and secondary weights eccentrically mounted on a power driven shaft, the primary weight being fixed to that shaft and the secondary weight being movable with respect to the shaft between a high amplitude position and a low amplitude position.

The machines of the aforesaid two patents are capable of reasonably good performance, but they leave room for improvement. To illustrate, while the vibration generator of the Tuneblom patent has the advantage of simplicity and few parts as a result of its capability of being switched from low to high amplitude vibration generation and vice versa by simply changing the direction of rotation of the power driven shaft on which its eccentric weights are mounted, the need for changing the direction of that rotation constitutes a serious disadvantage. It has been known for quite some time as evidenced by the German Pat. No. 1,255,591, which has a 1957 filing date that unless the direction of rotation of the eccentric weights is correlated with the direction the machine is travelling, the quality of the sur' face being compacted suffers. The reason for this as explained in the aforesaid German patent and also in US Pat. No. 3,605,583 lies in the fact that rotation of the eccentric mass in the same direction the drum turns during traverse of the machine promotes uniformity in compaction of the surface being worked, especially an asphalt surface, whereas rotation of the eccentric mass in the direction opposite that of the drum results in skipping and bumping of the drum and increases the tractive effort necessary for machine propulsion.

Thus if the objectionable consequences of not having the direction of rotation of the eccentric weights at all tage of the Tuneblom machine, and is capable of producing vibration in either the high or low amplitude mode regardless of the direction in which the machine is traveling so that the direction of rotation of the eccentric weights can be properly correlated with that of the drum, the hydraulic system employed in the Barrett et al. machine to effect a shift from one amplitude mode to the other introduces a significant elementof cost. v

The present invention combines the simplicity of the Tuneblom vibration generator with the versatility of the Barrett et al. machine and does so with a simple, reliable and inexpensive structure. Accordingly, the invention achieves a significant improvement in variable vibration generators.

As distinguished from the machine of the Tuneblom patent which undoubtedly is the most pertinent bit of prior art requiring consideration in evaluating the patentability of this invention the present invention enables the operator to at all times correlate the direction of rotation of the eccentric weights with the selected direction of travel, without constraining his choice between high and low amplitude vibration, since that choice does not necessitate changing the direction in which the eccentric weights revolve.

This advantage stems from the fact that when the vibration generator is not in operation, its eccentric weights automatically assume an in-phase relationship and that during initial rotation, in either direction, of the shaft on which the eccentric weights are mounted, relative motion automatically takes place between them from that in-phase relationship to an out-of-phase relationship which places the vibration generator in a low amplitude mode of the same magnitude regardless of the direction of rotation unless a simple mechanical operator-controlled locking device secures the secondary eccentric weights against such rotation relative to the shaft. This gives the operator a wide latitude of choice in the operation of the machine.

Another important feature of the invention resides in the .manner in which the movable secondary eccentric weights are locked or secured against displacement from a position in phase with the primary eccentric weights that are fixed to the shaft. This is done by acti vating a detent connected between the hubs of the movable secondary weights and the shaft while the shaft is stationary and the eccentric weights are in their in-phase relationship which they automatically assume when the shaft stops turning, the activation of the detent being effected by simplyshifting an actuator rod that is slidably received in an axial bore in the shaft.

Although the primary objective of the invention is the provision of an improved variable amplitude vibration generator by which either high or low amplitude vibration can be selectively produced with the eccentric weights rotating in either direction, it is also an object of the invention to provide a variable amplitude vibration generator capable of producing vibration in more than two modes and to accomplish this result with a simple, uncomplicated, rugged structure.

With the above and other objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the inven tion, it being understood that-changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims. 1

The accompanying drawings illustrate several complete examples of the embodiments of the invention constructed according to the best modes so far devised for the practical application of theprinciples thereof, and in which:

FIG. 1 is a front perspective view of a compacting machine equipped with one form of the variable amplitude vibration generator of this invention, attention being directed to the fact that there are actually two duplicate units to the generator both located within the surface rolling drum of the machine and that the drum is not driven;

FIG. 2 is a longitudinal sectional view through one of the units of the variable vibration generator embodied in the machine shown in FIG. 1',

FIG. 3 is a cross sectional view through FIG. 2 on the plane of the line 3-3, with the primary and secondary eccentric weights in their in-phase relationship;

FIG. 4 is a view similar to FIG. 3 but showing the eccentric weights in their out-of-phase relationship;

FIG. 5 is a longitudinal sectional view similar to FIG. 2, but illustrating the vibration generator embodied in a power driven drum;

FIG. 6 is a cross sectional view through FIG. 5 on the plane of the line 6--6;

FIG. 7 is a side view of a power driven drum with portions broken away and in section to especially illustrate the manner in which the drum and the shaft of the vibration generator are driven;

FIGS. 8 through 11 are a series of longitudinal sectional views through a variable amplitude vibration generator suitable for incorporation in the drum of a compacting machine, that is capable of operation in four different amplitude modes, each of said views showing the vibration generator in a different amplitude mode; and

FIG. 12 is a detail sectional view of a portion of the structure illustrated in FIGS. 8-11.

Referring now particularly to the accompanying drawings, and especially to FIGS. 1 through 4, the numeral 4 designates the chassis of a self-propelled surface compacting machine of the type employed in the paving of streets and roadways. The machine illustrated in FIG. I has a freely rotatable i.e. not power driven compacting drum 5 at its front end and a pair of power driven traction wheels 6 at its rear. As is customary, power is delivered to the traction wheels 6 from the power plant of the machine (not visible in FIG. 1) under control of an operator who occupies a seat 7 that is located behind a steering wheel 8 by which the operator steers the machine. For that purpose, the drum as sembly and the chassis of the machine are articulately connected for relative rotation about an upright axis. Details of the steering mechanism and of the reversible propulsion system through which power is delivered to the rear traction wheels being conventional and well known are not shown.

As is conventional, the drum assembly comprises a rigid yoke, the arms 9 of which embrace the drum and have bearing mounting plates 10 connected thereto by elastic shock mounts 11 (see FIG. 2). The bearing plates 10 are adjacent to the ends of the drum and have fixed thereto a cylindrical housing 12 in which the outer races of bearings 13 are mounted. The inner races of the bearings 13 are seated on the hubs 14 of the drum. In this manner the drum is freely rotatably connected with the mounting plates and, through the shock mounts 11, with the arms 9 of the yoke. Vibration of the drum is therefore not imparted to the rest of the machine. Although FIG. 2 shows only the aforesaid structure at one end of the drum, it is to be under stood that this same structure is duplicated at the other end of the drum. With that understanding, the following description will concern itself only with the structure at one end of the drum.

The drum 5 is hollow, as is customary, and each of its opposite end walls 15 has a cup-shaped housing 16 welded thereto. This housing is concentric with the drum and has a flange 17 that encircles the hub 14 of the drum bolted thereto. The inner end wall 18 of the housing 16 and the flange 17 that encircles the hub 14 have bearings 19 mounted therein. These bearings are coaxial and rotatably mount a tubular shaft 20 that extends for the full length of the drum and is coaxial therewith.

Mounted on the shaft 20 inside each housing 16 is one of the two units, designated generally by the numeral 21, of the variable vibration generator of this invention. The two units are identical. Each comprises a primary weight 22 that is eccentrically fixed to the shaft 20 as by being welded thereto and a secondary weight 23 freely eccentrically rotatably mounted on the shaft but securable thereto by a manually controllable detent type locking device to be described later. The primary weight consists of a pair of generally bellshaped plates 25 fixed to the opposite sides of an arcuate spacer block 26. One of the plates is welded to the spacer block and the other is secured thereto by cap screws 27. As shown in FIGS. 3 and 4, the spacer block 26 conforms in shape and size to the wide bottom edge portions of the bell shaped side plates. Preferably the arcuate spacer block and the bottom edge of the side plates are concentric with the shaft 20.

The upper stem portions 28 of the side plates which can be considered as arms that extend radially from the shaft 20 are connected by a cross bar 29, one end of which is welded to the side plate that is welded to the shaft. The other end of the cross bar is fixed to the adjacent side plate by a cap screw 30.

The secondary weight 23 is journalled on the shaft between the two side plates 25 and has its center of gravity spaced radially a substantial distance from the axis of the shaft so that the secondary weight hangs from the shaft in the position shown in FIG. 3 when the shaft is not turning. In fact, the primary weight also assumes the pendent position shown inFIG. 3 when the shaft is not turning. In that condition, the two eccentric weights occupy an in-phase relationship.

However, during initial rotation of the shaft in either direction, the primary weight moves away from its position in phase with the secondary weight and, after slightly less than of rotation of the shaft, the cross bar 29 collides with a lug 31 that projects from the arcuate edge 32 of the secondary weight and constitutes its radially outermost portion. Upon such collision, the eccentric weights are almost completely in out-ofphase relationship, as shown in FIG. 4. As long as the shaft continues to turn in the direction that brought about the collision of the cross bar 29 with the lug 31, the weights remain in their out-of-phase relationship. Since the secondary weight is lighter than the primary weight, it only partially counterbalances the primary weight, so that with the weights thus disposed the vibration generator is in its low amplitude mode.

Since, as shown in FIG. 3, the cross bar 29 and the lug 32 are symmetrically disposed with respect to a vertical plane coincident with the axis of the shaft, the angle through which the aforesaid relative rotation between the secondary weight and the shaft extends in effecting the described out-of-phase relationship is the same regardless of the direction of rotation. Hence the magnitude of the low amplitude vibration is the same for either direction of rotation.

The high amplitude mode is obtained by locking the secondary eccentric weight against rotation about the shaft from its position in phase with the primary weight, which position it automatically assumes when the shaft stops rotating. This is done by the previously mentioned detent-type locking device. As best shown in FIGS. 3 and 4, this locking device comprises a pair of coaxial detents or sockets 32 in diametrically opposite portions of the hub 33 of the secondary weight and a pair of locking balls 34 in the outer end portions of a cross bore 35 extending diametrically through the shaft. Both the detents and the cross bore are equispaced from the side plates 25 of the primary eccentric weight. Hence, the detents and the cross bore can be brought into alignment enabling the locking balls to be projected into the detents to secure the secondary weight to the shaft. That alignment obtains when the shaft is not turning and both weights are in the pendent position, as shown in FIG. 3. Absolute freedom for the secondary weight to assume a pendent position is assured by providing its hub with suitable anti-friction bearings 33 that are spaced apart to, in effect, form a circular groove 38 in the hub.

To enable assembly of the locking device, the detents or sockets 32 are in the inner ends of a pair of studs 36 threaded into coaxial tapped holes in the hub 33 and secured against displacement by lock nuts 37.

Preferably the cross bore 35 has its end portions lined by sleeves 39 that provide runways for the balls 34 and facilitate in and out movement of the balls.

The balls 34 are cammed out of the ends of the cross bore 35 and into the detents or sockets 32 by a conically shaped shoulder 40 on a rod 41 that is slidably re ceived in a bore 42 extending axially through the shaft 20. The shoulder 40 is formed by the step in the diameter of the rod. With the rod in a position at which its small diameter portion is aligned with the cross bore 35 in the shaft, the balls 34 are free to leave the detents or sockets 33 and roll around the circular annular groove 38 in the hub 32, but when the rod is shifted to bring its large diameter portion into alignment with the cross bore, the balls 34 are forced into locking engagement with the detents or sockets 32.

To avoid objectionably large dimensions for the locking balls and the cross bore, spacer balls 43 are interposed between the balls 34 and the rod 41.

Any suitable actuating means can be employed to shift the rod 41 to and from its position securing the eccentric weights in their in-phase relationship. For illustrative purposes, in FIG. 2 a fluid pressure cylinder 44 is mounted in fixed relation with the mounting plate 1 1. This cylinder is coaxial with the drum and its piston 45 is connected with the rod 41 through a rotation accommodating coupling 46. Fluid pressure delivered to the cylinder through a supply line 47 projects the piston 45 and the rod to the left (in FIG. 3) to cam the balls 34 into locking engagement with the detents or sockets 32. Retraction of the piston and the rod upon reduction of pressure in the cylinder is effected by a spring 48 reacting between the piston and the inner end of the cylinder.

As in the machine of the Barrett et al. US. Pat. No. 3,814,532, the two units of the variable amplitude vibration generator are mounted upon separate coaxial shafts connected by a torque tube to which they are joined by flexible couplings A reversible hydraulic motor mounted on the plate 10 at one-end of the drum,

is drivingly connected to the adjacent shaft 20 through a conventional flexible coupling. This motor is not shown in FIG. 2 but is indicated in dotted lines in FIG. 1 and also shown in FIGS. 5 and 7, in each of which it is identified by the numeral 50. FIGS. 5 and 7 also identify by the numeral 50' the flexible coupling through which driving torque is transmitted to the connected shafts 20 from the motor. Energization of the motor 50 as well as its direction of rotation is controllable in the customary manner by the operator of the machine, and as is also explained in the Barrett et al. patent selection of the direction of rotation of the motor is preferably automatically coordinated with the selection of the direction of traverse of the machine, so that the horizontal components of force resulting from operation of the vibration generator will not oppose propulsion of the machine.

In the embodiment of the invention just described and shown in FIGS. 14, the drum is not driven so that it does not contribute to the propulsion of the machine by the traction wheels 6. Obviously, of course, the variable amplitude vibration generator of this invention is also adaptable to a compacting machine in which the drum is driven. FIGS. 5-7 illustrate this adaptation of the invention. It differs from the structure just described only in the manner in which the control rod 41 is shifted and that difference is entailed by the fact that access to the outer ends of both shafts 20 is obstructed at one end by the hydraulic motor 50 and at the other end by a hydraulic motor 51 that drives the drum.

FIG. 7 illustrates the positional relationship between the two motors and the outer ends of the shafts 20.

The rod shifting mechanism in this embodiment of the invention comprises a fork 52 pivoted to swing about a fixed axis established by bearings 53 that are mounted in the wall of a cylindrical housing 54 that is connected to the adjacent bearing plate that is connected through shock mounts with the adjacent arm of the yoke 9, none of which structure appears in FIGS. 5 and 6. The cylindrical housing 54 corresponds to the housing 12 of the previously described structure (see FIG. 2) and has the outer race of one of the drum bearings 13 mounted therein.

The arms of the fork 52 are fixed to a tube 55 (see FIG. 6) which in turn is fixed to a shaft 56 that is journalled in the bearings 53 and has a lever 57 secured to one end thereof. That lever is connected to the plunger 58 of an air cylinder 59 pivotally anchored to a bracket 60 that is bolted to the housing 54. Hence, by controlled introduction of air pressure into the opposite ends of the cylinder59, the shaft 56 can be oscillated to rock the fork 52 from one position to the other of its range of motion defined by stops 61 and 62 that are mounted on the bracket 60.

The extremities of the arms of the fork 52 are bifurcated to receive trunnions 63 that project coaxially from a ring 64 formed of two half sections bolted together. This ring encircles a sleeve 65 that is slidably and freely rotatably mounted on the adjacent end portion 66 of the shaft 20. The ring 64 has a groove opening to its inner surface to receive a flange 67 on the sleeve and thereby freely rotatably connect the ring with the sleeve. Accordingly, upon rocking motion being imparted to the fork, the sleeve is shifted axially along the end portion 66 of the shaft 20. That axial motion of the sleeve is imparted to the rod 41 through a bolt 68 that passes through a cross bore in the adjacent end portion of the rod and slides in longitudinal slots 69 in the shaft portion 66, it being understood that the shaft 20 is tubular from end to end to accommodate the rod 41. By virtue of the bolt 68 being received in the slots 69, the rod 41, the shaft 20 and the sleeve 65 rotate in unison, such rotation being imparted thereto in the selected direction by the motor 50 which is drivingly connected to the shaft.

As will be readily apparent, with the actuating mechanism just described, the rod 41 can be shifted from its low amplitude position to its high amplitude position, despite the fact that the motor 50 obstructs access to the adjacent end of the rod.

To the extent that the structure shown in FIG. has not been described, it comports with that shown in FIG. 2, and accordingly is identified by the same reference numerals.

The two embodiments of the invention that have been described provide for only a low and a high amplitude of vibration, whereas in that embodiment of the invention shown in FIGS. 8-12, vibration at any of four different levels of amplitude can be had. In this fourmode system, there is a single primary eccentric weight 70 and two secondary eccentric weights a heavy one 71 and a light one 72. To accommodate the two secondary weights, the side plates 25' of the primary weight are farther apart than they are in the previously described two-mode vibration generator, and accordingly the crossbar 29 is longer, so that the crossbar will collide with either or both of the secondary weights during initial rotation of the drive shaft 20, depending upon which of the secondary weights is free to turn about the shaft.

The secondary weights are individually and selectively securable to the shaft by ball detent locking devices that are identical with that of the described twomode system, but for each unit of the vibration generator the rod 41' has two small diameter portions and four conical shoulders 40 formed by the steps between the small and large diameter portions of the shaft. These shoulders are so located with respect to each other and the hubs of the two secondary weights that in each of four different axial positions of the rod, a different amplitude of vibration is obtained. Thus, as indicated in FIG. 8, low amplitude vibration results when the heavier of the two secondary weights is free to assume an out-of-phase relationship with the primary weight and the lighter secondary weight is locked in its in-phase relationship with respect to the primary weight.

Minimum amplitude vibration results from having both secondary weights free to assume out-of-phase relationship with the primary weight, as illustrated in FIG. 9; medium amplitude vibration is obtained when only the lighter one of the two secondary weights is free to assume its out-of-phase relationship with the primary weight, as shown in FIG. 10; and high amplitude vibration is obtained when both secondary weights are locked to the shaft, as in FIG. 11.

While any suitable means may be employed to shift the rod 41 to its different positions shown in FIGS. 8-11, a multiple-position fluid pressure cylinder 80 has been found to be entirely satisfactory. Cylinders of this type are commercially available and, since it forms no part of the present invention, a detailed description thereof is not needed. Suffice it to say that the cylinder has four ports, designated A, B, C, and D, through which fluid pressure is introduced to selectively effect movement of the piston in the cylinder to each of four different positions, in each of which it holds the rod 41 in the position establishing the selected amplitude mode. The arrows opposite the different ports identify which of them that are connected with the source of fluid pressure to place the vibration generator in the amplitude mode shown in each of the four views of the series.

Inasmuch as the rod 41 rotates with the shaft 20, a rotation accommodating coupling 81 connects the rod with the rod 82 of the piston in the cylinder 80. FIG. 12 illustrates the construction of the coupling 81. As there shown, the coupling comprises a cup-shaped body that is connected to the rod 41 by a clevis 84 and contains a ball bearing 85. The outer race of the bearing is secured in the cup-shaped body and its inner race is secured to the piston rod 82.

As in the first described embodiment of the invention, in this four-amplitude version, the shaft 20 of the vibration generator is driven by a hydraulic motor at the end of the drum remote from that at which the shifting mechanism for the rod 41' is located.

Although the operation of the variable amplitude vibration generator of this invention is no doubt readily understandable from the foregoing description, a brief recapitulation may be welcome. With the machine stationary and the shaft on which the eccentric weights are mounted not turning, the weights are in their inphase pendent positions (FIG. 3). For low amplitude vibration, the secondary lighter weights must be free to turn with respect to the shaft. That assured, upon initial rotation of the shaft, the primary eccentric weights rotating therewith will be moved from in-phase towards out-of-phase relationship with the secondary eccentric weights. After somewhat less than of rotation, the primary weights collide with the secondary weights and then they move in unison. This takes place automatically whether the shaft rotates clockwise or counterclockwise, and as long as the shaft continues to rotate in the selected direction, the primary and secondary weights remain in their out-of-phase partially counterbalancing relationship and produce low amplitude vibration of the same magnitude regardless of the direction of rotation.

If high amplitude vibration is selected, the secondary weights are simply secured against rotation about the shaft in their in-phase relationship with the primary weights, that securement being effected by activating the ball detents.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims:

I claim:

1. A variable amplitude vibration generator comprising:

A. a rotatably mounted shaft;

B, a primary weight eccentrically fixed to the shaft to rotate therewith;

C. a lighter secondary weight;

D. means freely rotatably mounting the secondary weight eccentrically on the shaft, said weights occupying pendent in-phase positions when the shaft is not turning;

E. power means to impart rotation to the shaft in either direction;

the freedom for relative rotation between the secondary weight and-the shaft enabling the secondary weight to remain in its pendent position while the shaft begins to turn and moves the primary weight out of phase with the secondary weight; and y F. means to limit relative rotation in eitherdirection between the shaft and the secondary weight to substantially less than 360, so that upon-rotation of the shaft in either selected direction, the two weights become connectedin an out-of-phase partially counter-balancing relationship placing the vibration generator in a low amplitude mode of substantially the same magnitude regardless of the direction of rotation which mode it retains as long as .the shaft continues to turn in said selected direction. v

' 2. The variable amplitude vibration generator of claim I wherein relative rotation in either direction betweenthe shaft and the secondary weight is limited to a few degrees less than 180 so that in each case said out-of-fphase relationship is slightlylessthan complete.

3. The variable amplitude vibration generator of claim 1', further characterized by detent meansfor 're'leasably securingthe secondary weight against rotation relative to the shaft in a pos'ition' in which it is in phase with. the primary weight, so that upon rotation of the shaft while the secondary weight is thus secured thereto the vibration generator operates in a high amplitude mode. .4. The, variable amplitude vibration generator of claim 1, wherein f the center of gravity' of the primary weight and the means to limit relative rotation between the shaft and the secondary weight are at opposite sides of the shaft and wherein said means tolimit relative rotation between the shaft and the secondary weight comprises: i i 1. an arm fixed with respect to andprojecting radially from the shaft; and. 2. an abutment on said arm in position with a surface on the secondary weight that spacedfrom the axis of the shaft. 5. The variable amplitude vibration claim 4 wherein said surface with which said'abutment generator of to collide collides is on a lug that projects from the radially outermost portion of the secondaryweight. 6. The variable amplitude vibration 8. The variable amplitude vibration generator of claim 3, wherein the secondary weight has a hub in the bore of which the shaft is freely rotatably received,

and wherein said detent means comprises:

1. socket means in said hub and in the shaft which align with one another when the two weights are in phase;

2. a locking member movably received in the socket means in the shaft for movement between a retracted position disengaged from the socket means in said hub and a projected position engaging both socket means; and

3. actuating means longitudinally shiftably carried by the shaft to move said locking member to and hold it in its projected position.

9. The variable amplitude vibration generator of claim 8, wherein the socket means in said hub comprises diametrically opposite sockets opening to the bore of the hub,

wherein the socket means in the shaft comprises a cross bore extending diametrically through the shaft,

and wherein said locking member comprises a ball in each end portion of said cross bore.

10. The variable amplitude vibration generator of claim 9, wherein said actuating means comprises a round rod slidable'in anaxial bore in the shaft that intersects said cross bore, said rod having large and small diameterportions either of which can be brought into alignment with the cross bore by axially shifting the rod, so that in one axial position of the rod with respect to the shaft, said balls are free to leave engagement with the sockets in said hub, while in another axial position of the rod the balls are held seated in said sockets in the hub.

11. The variable amplitude vibration generator of claim 10, further characterized by a means for imparting axial movement to saidrod with respect to the shaft.

'12. The variable amplitude vibration generator of claim 11, wherein. at least one of the steps between the large andsmall diameter portions of the shaft is conical, so that during axial movement of the rod in the di- I rection to align its large diameter portion with which said conical step connects, with the cross bore, said step serves as a cam to effect projection of the balls into member with spaced arms that have a fixed connection with the shaft and that project radially from the shaft in the same direction, i I

and wherein the secondary weight is located between said arms.

7. The variable amplitude vibration generator of claim 6, wherein the means to limit relative motion between the shaft and the secondary weight comprises:

i 1. an extension on each of said spaced arms projecting radially from the shaft in the direction opposite that in which said spaced arms project from the shaft;

2. a crossbar connecting the outer end portions of said extensions; and

3. a lug on the secondary weight spaced from the axis of the shaft a distance to have said crossbar collide therewith upon rotation of the shaft in either direction.

said sockets in the'hub'.

13. The variable. amplitude vibration generator of claim-12, whereina second pair of balls is located in said cross bore,'one between each of the first named balls and the rod. I

, 14. The variable amplitude vibration. generator of claim 11, wherein the means for imparting endwise movement to the rod comprises a fluid pressure cylinder fixed against movement axially of the'shaft, and a piston in the cylinder connected with the rod to impart movement thereto upon connection of the cylinder with a source of fluid pressure.

15. The invention defined by claim 11, further characterized in that the variable amplitude vibration generator is associated with a compacting machine having a frame and a drum rotatably and supportingly connected with the frame, with the shaft of the vibration generator coaxial with and inside the drum,

wherein said means for imparting axial movement to the rod is carried by the frame of the machine at one end of the drum, and wherein said power means to impart rotation to said shaft is carried by the frame of the machine at the other end of the drum.

16. The variable amplitude vibration generator of claim 11,

wherein the variable amplitude vibration generator is associated with a compacting machine having a frame and a drum rotatably and supportingly connected with the frame, with the shaft of the vibration generator coaxial with and inside the drum, wherein a motor carried by the frame of the machine at one end of the drum is drivingly connected with the drum to impart rotation to the drum, wherein a motor carried by the frame of the machine at the other end of the drum is coupled to the shaft of the vibration generator to impart rotation to it, and wherein said means for imparting axial movement to the rod is carried by the frame of the machine at said last named end of the drum, and so located that it does not interfere with the driving connection between the shaft of the vibration generab r and its motor.

17. The variable amplitude vibration generator of claim 3, wherein there are a plurality of secondary weights eccentrically freely rotatably mounted on the shaft, and separate detent means for each secondary weight, so that by selective actuation of said separate detent means, the vibration generator can be set to produce vibration at more than two different amplitudes.

18. The variable amplitude vibration generator of claim 17, wherein the secondary weights differ in weight.

19. The variable amplitude vibration generator of claim 17, wherein there is but one primary weight that is heavier than any of the secondary weights.

20. The variable amplitude vibration generator of claim 19, wherein A. there are two secondary weights each of which is eccentrically'mounted n the shaft by a hub in the bore of which the shaft is freely rotatably received, and detent means for releasably securing said hub against rotation relative to the shaft;

B. wherein said detent means comprisesv l. a socket opening to the bore of said hub,

2. a radial bore in the shaft opening to the surface thereof that is within the hub to align with the socket in the hub, and

3. a movable element in said radial bore movable between an operative position projecting into the socket and an inoperative position free of the socket in the hub, the shaft having an axial bore which communicates with said radial bore;

C. a rod axially slidable in said axial bore, said rod having a small diameter portion flanked by large diameter portions for each of said two secondary weights, alignment of a small diameter portion of the rod. with a radial bore enabling said movable element therein to move to its inoperative position, and alignment of a large diameter portion of the rod with said radial bore holding said movable element in its operative position, said small diameter portions of the rod being so spaced with respect to one another and the two secondary weights, and being of such length that l. in one axial position of the rod the hubs of both of said secondary weights are secured to the shaft,

2. in a second position of the actuating rod neither of the hubs of the secondary weights is secured to the shaft,

3. ina third position of the rod only the hub of the heavier of the two secondary weights is secured to the shaft, and

4. in a fourth position of the rod only the hub of the lighter one of the two secondary weights is secured tothe shaft; and

D. means for selectively moving the rod to any one of said four positions. v

21. The variable amplitude vibration generator of claim 20, wherein said radial bore of each of the detent means is a cross bore extending through the shaft,

wherein the hub of each secondary weight has two diametrically opposite sockets opening to its bore, and.

wherein each detent means has two balls, one in each end portion of its cross bore.

Claims

1. A variable amplitude vibration generator comprising: A. a rotatably mounted shaft; B. a primary weight eccentrically fixed to the shaft to rotate therewith; C. a lighter secondary weight; D. means freely rotatably mounting the secondary weight eccentrically on the shaft, said weights occupying pendent inphase positions when the shaft is not turning; E. power means to impart rotation to the shaft in either direction; the freedom for relative rotation between the secondary weight and the shaft enabling the secondary weight to remain in its pendent position while the shaft begins to turn and moves the primary weight out of phase with the secondary weight; and F. means to limit relative rotation in either direction between the shaft and the secondary weight to substantially less than 360*, so that upon rotation of the shaft in either selected direction, the two weights become connected in an out-of-phase partially counterbalancing relationship placing the vibration generator in a low amplitude mode of substantially the same magnitude regardless of the direction of rotation which mode it retains as long as the shaft continues to turn in said selected direction.

2. The variable amplitude vibration generator of claim 1, wherein relative rotation in either direction between the shaft and the secondary weight is limited to a few degrees less than 180 so that in each case said out-of-phase relationship is slightly less than complete.

2. an abutment on said arm in position to collide with a surface on the secondary weight that is spaced from the axis of the shaft.

2. a crossbar connectinG the outer end portions of said extensions; and

3. a movable element in said radial bore movable between an operative position projecting into the socket and an inoperative position free of the socket in the hub, the shaft having an axial bore which communicates with said radial bore; C. a rod axially slidable in said axial bore, said rod having a small diameter portion flanked by large diameter portions for each of said two secondary weights, alignment of a small diameter portion of the rod with a radial bore enabling said movable element therein to move to its inoperative position, and alignment of a large diameter portion of the rod with said radial bore holding said movable element in its operative position, said small diameter portions of the rod being so spaced with respect to one another and the two secondary weights, and being of such length that

3. in a third position of the rod only the hub of the heavier of the two secondary weights is secured to the shaft, and

3. The variable amplitude vibration generator of claim 1, further characterized by detent means for releasably securing the secondary weight against rotation relative to the shaft in a position in which it is in phase with the primary weight, so that upon rotation of the shaft while the secondary weight is thus secured thereto the vibration generator operates in a high amplitude mode.

4. The variable amplitude vibration generator of claim 1, wherein the center of gravity of the primary weight and the means to limit relative rotation between the shaft and the secondary weight are at opposite sides of the shaft and wherein said means to limit relative rotation between the shaft and the secondary weight comprises:

4. in a fourth position of the rod only the hub of the lighter one of the two secondary weights is secured to the shaft; and D. means for selectively moving the rod to any one of said four positions.

5. The variable amplitude vibration generator of claim 4 wherein said surface with which said abutment collides is on a lug that projects from the radially outermost portion of the secondary weight.

6. The variable amplitude vibration generator of claim 1, wherein the primary weight is a U-shaped member with spaced arms that have a fixed connection with the shaft and that project radially from the shaft in the same direction, and wherein the secondary weight is located between said arms.

8. The variable amplitude vibration generator of claim 3, wherein the secondary weight has a hub in the bore of which the shaft is freely rotatably received, and wherein said detent means comprises:

9. The variable amplitude vibration generator of claim 8, wherein the socket means in said hub comprises diametrically opposite sockets opening to the bore of the hub, wherein the socket means in the shaft comprises a cross bore extending diametrically through the shaft, and wherein said locking member comprises a ball in each end portion of said cross bore.

10. The variable amplitude vibration generator of claim 9, wherein said actuating means comprises a round rod slidable in an axial bore in the shaft that intersects said cross bore, said rod having large and small diameter portions either of which can be brought into alignment with the cross bore by axially shifting the rod, so that in one axial position of the rod with respect to the shaft, said balls are free to leave engagement with the sockets in said hub, while in another axial position of the rod the balls are held seated in said sockets in the hub.

11. The variable amplitude vibration generator of claim 10, further characterized by means for imparting axial movement to said rod with respect to the shaft.

12. The variable amplitude vibration generator of claim 11, wherein at least one of the steps between the large and small diameter portions of the shaft is conical, so that during axial movement of the rod in the direction to align its large diameter portion with which said conical step connects, with the cross bore, said step serves as a cam to effect projection of the balls into said sockets in the hub.

13. The variable amplitude vibration generator of claim 12, wherein a second pair of balls is located in said cross bore, one between each of the first named balls and the rod.

14. The variable amplitude vibration generator of claim 11, wherein the means for imparting endwise movement to the rod comprises a fluid pressure cylinder fixed against movement axially of the shaft, and a piston in the cylinder connected with the rod to impart movement thereto upon connection of the cylinder with a source of fluid pressure.

15. The invention defined by claim 11, further characterized in that the variable amplitude vibration generator is associated with a compacting machine having a frame and a drum rotatably and supportingly connected with the frame, with the shaft of the vibration generator coaxial with and inside the drum, wherein said means for imparting axial movement to the rod is carried by the frame of the machine at one end of the drum, and wherein said power means to impart rotation to said shaft is carried by the frame of the machine at the other end of the drum.

16. The variable amplitude vibration generator of claim 11, wherein the variable amplitude vibration generator is associated with a compacting machine having a frame and a drum rotatably and supportingly connected with the frame, with the shaft of the vibration generator coaxial with and inside the drum, wherein a motor carried by the frame of the machine at one end of the drum is drivingly connected with the drum to impart rotation to the drum, wherein a motor carrieD by the frame of the machine at the other end of the drum is coupled to the shaft of the vibration generator to impart rotation to it, and wherein said means for imparting axial movement to the rod is carried by the frame of the machine at said last named end of the drum, and so located that it does not interfere with the driving connection between the shaft of the vibration generator and its motor.

20. The variable amplitude vibration generator of claim 19, wherein A. there are two secondary weights each of which is eccentrically mounted on the shaft by a hub in the bore of which the shaft is freely rotatably received, and detent means for releasably securing said hub against rotation relative to the shaft; B. wherein said detent means comprises

21. The variable amplitude vibration generator of claim 20, wherein said radial bore of each of the detent means is a cross bore extending through the shaft, wherein the hub of each secondary weight has two diametrically opposite sockets opening to its bore, and wherein each detent means has two balls, one in each end portion of its cross bore.