US3832080A

US3832080A - Vibrator, especially a self propelled reversible tamper

Info

Publication number: US3832080A
Application number: US00267127A
Authority: US
Inventors: K Stoecker
Original assignee: HEINRICH MACHINERY AND TOOL Manufacturing
Current assignee: HEINRICH MACHINERY AND TOOL Manufacturing
Priority date: 1972-06-28
Filing date: 1972-06-28
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

A vibrator, especially a self propelled reversible tamper having a base plate that is turned up at both ends, comprising a housing, a driving shaft and a driven shaft journaled in the housing, each shaft having an eccentric mounted thereon and a gear on each shaft for rotating them in opposite directions at the same speed. The eccentric on one shaft has a fixed connection with respect to its gear in a single angular relation thereto. The eccentric on the other shaft has a selective connection with respect to its gear in a plurality of angular relations thereto and the selective connection can be changed by suitable means from one angular relation to another during operation of the vibrator. This enables the tamper to be self propelling in two opposite directions. A handle pivoted to the base plate for movement through an arc from an operating position at one end to an operating position at the opposite end of the base plate may be provided to guide the moving tamper.

Description

United States Patent [191 Stoecker [451 Aug. 27, 1974 YVIBRATOR, ESPECIALLY A SELF PROPELLED REVERSIBLE TAMPER Karl M. Stoecker, Mt. Arlington, NJ.

221 Filed: June 28,1972

211 Appl. No.: 267,127

[75] Inventor:

[52] US. Cl. 404/133, 74/61 10/1968 Germany 74/61 5/1942 Switzerland 74/61 Primary Examiner-Marion Parsons, Jr. Attorney, Agent, or Firm-George I-I.- Mortimer [57] ABSTRACT A vibrator, especially a self propelled reversible tamper having a base plate that is turned up at both ends, comprising a housing, a driving shaft and a driven shaft journaled in the housing, each shaft having an eccentric mounted thereon and a gear on each shaft for rotating them in opposite directions at the same speed. The eccentric on one shaft has a fixed connection with respect to its gear in a single angular relation thereto. The eccentric on the other shaft has a selective connection with respect to its gear in a plurality of angular relations thereto and the selective connection can be changed by suitable means from one angular relation to another during operation of the vibrator. This enables the tamper to be self propelling in two opposite directions. A handle pivoted to the base plate for movement through an are from an operating position at one end to an operating position at the opposite end of the base plate may be provided a PATENTEDAUEEYIQH PATENTEB 7 33. 8'82. 080

VIBRATOR, ESPECIALLY A SELF PROPELLED REVERSIBLE TAMPER SUMMARY OF THE INVENTION The invention relates to a vibrator having at least two shafts rotating in opposite directions with eccentrics mounted thereon which generate a force having both vertical and horizontal components. The direction of the horizontal component can be changed so that the vibrator tends to move in one direction or the opposite direction by suitable means for changing the angular relation of the eccentric on one shaft .with respect to the angular relation of the eccentric on the other shaft. Preferably the vibrator is mounted on the base plate of a tamper, the base plate being provided with up turned ends and having a motor, preferably an internal combustion engine, mounted thereon to provide the driving force for rotating the shafts in the vibrator of the tamper. A handle is preferably provided to guide the tamper as it moves back and forth over the surface to be compacted and it may be pivoted to the baseplate so that it can be swung from an operative position at one end of the base plate to an operative position at the other end thereof. Each shaft has a gear on it and they are in driving connection, e.g., by being in mesh one with the other, for rotating the shafts in opposite directions at the same speed. The means for changing the angular relations of the eccentrics may include mounting the eccentric weight on one of the shafts in a fixed relation to the gear thereon so that they rotate on their common shaft in a single angular relation to each other while the eccentric weight on the other shaft has a selective connection to the gear in a plurality of different angular relations thereto. This angular relation is capable of being changed by suitable means while the shafts are rotating and thereby change the direction of the horizontal component of force.

BACKGROUND OF THE INVENTION Vibrators using eccentric weights on a plurality of shafts are known in the art and they have been used for various purposes, e.g., for vibrating screens and for compacting earth either as part of a road roller or as a part of a tamper.

Some of the vibrators of the prior art provide for ad justment of the angular relation between eccentrics on parallel shafts rotating at the same speed in opposite directions so as to modify the amplitude and/or direction of the vibrating force. It has been proposed to mount such a vibrator on a base plate for ajarring machine on which a motor, e.g., an internal combustion engine, is also mounted which has a chain drive for the gears on the respective shafts in which the length of the,

run of the chain from one'gear to the other can be changed so as to alter the angular relation of the eccentric on one shaft with respect to the eccentric on the other. This is a relatively complex and costly arrangement which it is difficult properly to lubricate and maintain.

It has also been proposed to mount the vibrator in pivotal relation to the base plate so that it can be tilted in one direction or the other in order to give a horizontal component in selected opposite directions to make the tamper self propelling. The proposal has the difficulity of imparting the vibratory force through a journal at each end of the pivotally mounted vibrator which subjects the bearings to very high stress which is expensive to manufacture and to maintain.

DETAILED DESCRIPTION OF THE INVENTION The present invention overcomes the disadvantages and difficulties of the prior art by providing a selective connection of the eccentric weight on one of a pair of rotating shafts with respect to the gear for rotating it in a plurality of angular relations thereto and means for changing the selective connection from one angular relation to the other while the shafts are rotating. This arrangement makes it possible to mount the housing directly on the base plate so as to transmitt the vibratory force from the housing directly to the base plate. The horizontal component of the vibratory force can thus be directed by simple adjustment of a reversing lever to move the tamper in the desired direction. The housing is made fluid tight so that it can contain oil to keep the moving parts well lubricated. Preferably a handle is provided that has operating positions at both ends of the base plate and it can be swung in an are from one operating position to the other so as to guide the tamper as it moves itself across the earth to be compacted.

The best and preferred embodiment of the invention presently known is in the form of a tamper but it will be understood that the vibrator constructed in accordance with the principles of this invention may be used for other purposes. The tamper is illustrated .in the accompanying drawings in which:

FIG. I is a side view of a tamper with parts broken away to show internal structure;

'FIG. 2 is a end view of the tamper with the lower portion in vertical section along the line 22 of FIG. 1;

FIG. 3 is a horizontal section of the vibrator;

FIG. 4 is a plan view of the engine'mount showing the gear shift levers;

FIG. 5 is a fragmentary plan of the gear shift crank and disc with the driving and driven gears;

FIG. 6 is a vertical sectional view through a portion of the housing along the line 66 of FIG. 5;

FIG. 7 is a schematic representation of the tamper in four different positions of the eccentric shafts which have an angular relation with respect to each other that produces a horizontal component tending to move the tamper to the left;

FIG. 8 is a similar schematic view having the eccentrics arranged in a different angular relation with respect to each other that produces a horizontal component tending to move the tamper to the right.

Referring now to FIG. 1, the tamper 1 comprises a base plate 2, a vibrator 3, a motor mount 14, a motor 15 and a handle 16.

The base plate 2, as seen in FIGS. 1 and 2, comprises a flat central portion 21 having upwardly sloping ends 22 and side walls 23. The side walls have a top edge 24 parallel at the central portion to the flat central portion 21 of the base plate and similar circular bosses 25 adjacent to the upturned ends 22, each of which is provided with a bore 26.

Referring now to FIGS. 2 and 3, the vibrator 3 includes a frame or housing comprising

side walls

30 and 31,

end walls

32 and 33 and a top wall 34. The frame or housing can be cast from suitable metal as a unitary piece or it can be built up from metal plate by welding the parts together. The bottom of the housing should be closed to form a reservoir for oil to lubricate the rotating parts soon to be described. This may be accomplished by welding the side walls to a bottom plate and then securing the vibrator to the base plate in any suitable way but it is preferred to eliminate a bottom plate and to secure the side and end walls, e.g.,by welding, directly to the central portion 21 of the base plate in fluid tight relation. The base plate thus forms a bottom wall for the housing and provides a reservoir in which lubricant canbe placed to lubricate all of the moving parts, as more fully described hereinafter.

Side wall 30 has a large aperture 35 axially aligned with a small aperture 36 in side walls 31 toward one end thereof and a small aperture 37 axially aligned with a large aperture 38 in side wall 31 toward the other end thereof. A large cover 39 is secured in large. aperture 35 by means of cap screw 40 (only one is shown) and it is provided with a small aperture 41, preferably shouldered, which is axially aligned with the small aperture 36 in side wall 31. A small cap 42 is secured in aperture 41 by means of cap screws 43 (only one is shown). A small cover 44 is secured in small aperture 36 in side wall 31 by similar cap screws (not shown). A large cover 45 is secured in large aperture 38 by cap screws (not shown) and it is provided with a small aperture 46, preferably shouldered, in which a small cover 47 is secured by suitable cap screws (not shown). Small aperture 46 is aligned with small aperture 37. Self aligning roller bearings 48 are provided in

apertures

36 and 41 and similar roller bearings 49 are provided in apertures 37 and 46.

A shaft 50 is mounted in bearings 49 which has a central portion 51 of largest diameter on which a gear 52 having teeth 53 is mounted in nonrotational relationship by means of key slots 54 in the shaft and gear and a key 55 therein. At each side of the central portion 51 of shaft 50 is an intermediate portion 56 of reduced diameter. On each intermediate portion 56 eccentric weight 57 is secured in nonrotatable relationship by means of key slots 58 in the shaft and the weight, and a key 59 therein. Spacers 60, e.g., in form of collars, may be provided on the shaft 50 to locate the gear and eccentrics in proper spaced relation one from the other and from the bearings 49.

Shaft 50 is also provided with a journal portion 61 at each end of still further reduced diameter which fits properly in the bearings 49.

At one end of shaft 50 is a pulley extension 62 of still further reduced diameter on which a V-belt pulley 63 is keyed or otherwise secured in nonrotatable relationship with respect to shaft 50. A suitable cover 64 is secured to the housing, e.g., by cap screws (not shown),

. and it is provided with an aperture 65, preferably shouldered, to receive a sea] 66 to prevent leakage of lubricant from the housing through the aperture 37 and the parts associated therein. A slinger 67 is preferably mounted on the pulley extension 62 over the seal 66, as clearly shown in FIG. 3.

A shaft 68 is suitably mounted in bearings 48 and it comprises a central portion 69 of largest diameter on which a sleeve 70 is mounted in a slidable and rotational relationship. A gear 71 is mounted on sleeve 72 in nonslidable relation thereto by any appropriate means, e.g., by a shoulder 71a at one side and a split ring 71b at the other. The gear 71 has a driving connection with gear 52, e.g., by having teeth 72 in mesh with teeth 53. Gear 71 is preferably made somewhat thinner than gear 52 so that when sleeve 70 is at one limit of its sliding motion on central portion 69 its one face is aligned with the corresponding face of gear 52 and when the sleeve 70 is at the opposite end of its sliding motion the other face of gear 71 is aligned with the other face of gear 52. A driving pin 73 is mounted in a bore 74 at one side of gear 71 and a driving pin'75 in a bore 76 is mounted at the other side of gear 71. The driving pins 73 and 75 are fixedly secured in gear 71, e.g., by welds 77. Shaft 68 is provided with an intermediate portion 78 of reduced diameter at each end of the central portion 69. An eccentric 79 is mounted on one of these intermediate portions 78, e.g., by means of a key 80, in nonrotational relationship with respect to the shaft. Eccentric 79 is provided with a-driven pin 81 in the surface facing the gear 71 in a bore 82 at the same radial distance from the axis of the shaft as bore 74 in gear 71 and it is suitably secured in the eccentric, e.g., by a weld 83.

An eccentric 84 is suitably secured in nonrotational relationship to shaft 68 on the opposite intermediate portion 78, e.g., by a key 85. A driven pin 86 is mounted in eccentric 84 in a bore 87 at a radial dis tance from the shaft equal to the radial distance of bore 76 and pin 86 is suitably secured in its eccentric, e.g., by a weld 88.

As seen in FIG. 3, driving pin 75 has a length which clears eccentric 84 but engages driven pin 86 when sleeve 70 is at its upper limit of movement. Similarly pin 86 hasa length which clears gear 71 in its closest relationship thereto-but pins 75 and 86 are clear ,of each other when sleeve 70 is moved to the opposite end of central portion 69. Driven pin 73 likewise has a length which clears eccentric 79 when they are most closely related but engages driven pin 81. Pin 81 likewise is of such a length as to clear gear 71 when in closest relationship thereto but to engage driving pin 73.

The surfaces of the driving pins and driven pins which contact are preferably flattened for about half of the diameter of the pin so as to provide maximum area of contact with minimum wear for the purpose to be described.

Shaft 68 is provided at each end with a further reduced portion 89 which makes suitable engagement with bearings 48.

From the foregoing description of the rotating parts it will be seen that with small cover 64 secured in place, shaft 50 and all internal parts mounted thereon can be assembled outside the housing, bodily inserted through large opening 38, large cover 45 secured in place, slinger 67 slipped on the exposed end 62 and finally pulley 63 secured in place. Similarly shaft 68 and all parts secured thereto can be assembled externally and installed through large opening 35. If repairs are required, access to the parts is readily had by removal of shafts 50 and/or 68 by reversing the foregoing operatrons.

Provision is made of suitable gear shift means for shifting gear 71 from its position on shaft 68 shown in F IG. 3 at one limit of its sliding movement where driving pin 75 is in contact with driven pin 86 but driving pin 73 is clear of driven pin 81 to the opposite limit of its motion along shaft 68 in which driving pin 73 ably mounted in a bushing 92 suitably secured to the top wall 34 through an aperture, e.g., by welding, as shown clearest in FIG. 6. A shift lever 93 is secured in nonrotatable relation at the upper end of bolt 9], e.g., by being welded to the cap 94 thereof, as seen in FIG. 6. Between bushing 92 and shift lever 93 is a bronze washer 95 to reduce friction and a Y-seal 96 is desirably used around bolt 91 beneath washer 95, e.g., in a rabbet 97 in bushing 92. Between bushing 92 and disc 90 is a Belleville washer 98 to prevent jumping of the disc 90 when the washer 98 is compressed by screwing nut 99 on the threaded lower end of bolt 91, preferably with a split lock washer 100 between disc 90 and nut 99. To prevent nut 99 from loosening with the vibration, a lock means 101 of any suitable kind is preferably used in addition to the lock washer 100. Two shift pins 102 and 103 are suitably secured near the periphery of disc 90, e.g., through bores and then welded in place, as seen best in FIG. 6, at a spacing just sufficient to clear gear 71.

Referring now to H05. 2 and 5 it will be seen that disc 90 is provided with two

adjacent notches

104 and 105. A spring pressed ball 106 is mounted in'a bore in one end of a cap screw 107 which is screwed into a suitably located tapped bore 108 in side wall 30 of the housing so as to place the ball 106 in removable engagement with a selected

notch

104 or 105.

It will be seen that if shift lever 93 is moved counterclockwise from the position shown in FIG. 5, disc 90 will also move counterclockwise, moving ball 106 out of notch 105 and permitting it to seat in notch 104 after movement of a few degrees. This movement is just sufficient to shift gear 71 from its left limit to the right limit by engagement of pin 102 with the left side of the gear. The reverse action takes place on clockwise movement of shift lever 93 when ball 106 is seated in notch 104, pin 103 in this instance engaging the right side of gear 71 and shifting it to the left.

Any suitable means may be provided to move shift lever 93 in the manner described, and one such means that is now preferred is shown in FIG. 4 which comprises a shift bar 111 having a notch 112 centrally thereof in which the free end of shift lever 93 is located so that reciprocating longitudinal movement of bar 1 11 causes 93 to move clockwise or counterclockwise as the case may be. Bar 111 is secured at its ends in shackles 113 that are supported in identical levers 114 that are secured by cap bolts 115 to the underside of an engine base plate 140, soon to be described. Each lever 114 has a kick plate 116 integral with or fastened thereto at each end and for convenience of reference they are designated a, b, c and d. Looking at FIG..4 it will be seen that by kicking plate 116a or 1160 bar 111 will be moved to the right causing shift lever 93 to move clockwise. From the position thus assumed by the parts, they may be returned to the position shown in FIG. 4 by kicking

plates

116b or 116d.

The proper operation and low maintenance cost of the vibrator 3 requires proper lubrication and, as indicated above, the fluid tight connection of the housing with the base plate 2 will provide such an oil reservoir 124. Oil to the reservoir can be provided in any suitable way, e.g., by providing a cap screw 127 at a suitable level in a tapped bore 128 in end wall 32. Oil may be drained or removed from the reservoir 124 in any suitable way if need arises, e.g., if repair of the rotating parts is required, by standing the device upright with plug 127 removed and bore 128 at the bottom, or by removing either

large cover

39 or 45 and pouring the oil out of opening 35 or 38. Of course a drain plug could be provided if desired.

The motor mount 14 comprises a top plate having a flange 141 at the right end thereof, as seen in FIG. 2, and a flange 142 at the other end thereof which is provided with a cut out 143 for a purpose soon to be described. The motor mount is connected to the'basc plate in any suitable way, e.g., by providing four bosses 144, each engaged at one end with a semicircular boss 25 aligned with the bore 26 to receive a cap screw 145. Bosses 144 may be made of suitable material, e.g., rubber, metal, etc. Plate 140 must be far enough above top wall 34 when so mounted to provide space for the gear shift means described above.

The motor 15 is secured in any suitable way to top plate 140. While any suitable motor may be provided, it is preferred that it be an internal combustion engine type .which may have a suitable casing on which to mount a fuel tank 151 and to provide an aperture through which may pass a drive shaft 152, e.g., the crank shaft of an internal combustion engine, on which a V-pulley 153 is mounted in nonrotational relationship. A V-belt 154 connects V-pulley 153 with V-belt pulley 63 on shaft 50 and the V-belt operates through the cut out 143 in the motor mount plate.'A guard may be provided, if desired, around the V-belt as those skilled in the art will readily understand.

The mount for the handle 16 comprises, at each side, a handle support bar having ends 161 secured to

flanges

141 and 142, respectively, of the motor mount plate 140. This arrangement gives proper spacing between the handle support bar 160 and the motor

mount plate flanges

141 and 142. Each support bar 160 has a tapped bore 162 to receive a cap shoulder screw 163 on which a bushing 164 is rotatably mounted. Secured to the respective bushings 164 are the two ends of a U- shaped handle 165. Also secured to bushing 164, and opposite from the handle 165, is a limit arm 166 having a pin 167 extending inwardly therefrom so as to contact the undersurface of handle support bar 160 and thereby limit the rotation of the handle in downward direction at each side of its swinging movement in an are over the motor 15.

In operation of the device as a tamper, the internal combustion engine is started which causes the V-pulley 153 to drive V-belt pulley 63 and its related shaft 50. This causes eccentric weights 57 and gear 52 to rotate therewith and the rotation of gear 52 causes gear 71 to rotate at the same speed but in the opposite direction. Assuming that collar 70 occupies the position shown in FIG. 3 with-ball 106 in notch 105 and

parts

93 and 111 in the position shown in FIG. 4, rotation of gear 71 also causes eccentric 84'and shaft 68 to rotate therewith and at the same rate by contact of driving pin 75 with driven pin 86. Eccentric 79 rotates with eccentric 84,

since both are keyed to shaft 68, and in the same angular relation to eccentric weights 57 as eccentric 84. Assuming that this relationship places the

counterweights

79 and 84 in the angular relation to counterweights 57 shown in FIG. 7, the force components indicated by the arrows on the counterweights tend .to drive the base plate downwardly to compact the earth beneath it in the upper view, to lift it and move it to the left as the counterweights move to the positions shown in the second and third views,'and finally downwardly to compact the earth now under the baseplate as the eccentrics move from the position in the third view through the position shown in the forth view to arrive again in the position shown in the top view.

When the tamper has been guided by handle 165 to the end of the area to be compacted, the operator kicks plate 1160 to move the shift bar 111 to the other opposite operating position, thereby moving disc 90 until the spring loaded ball 106 enters the other notch 105. This disengages pins 75 and 86 while the parts are still rotating and brings driving pin 73 into contact with driven pin 81 in the new angular relationship of the

eccentrics

79 and 84 with respect to eccentrics 57 on shaft 50. This shifts the horizontal component of the vibrating force from the relationship causing movement to the left, as illustrated in FIG. 7, to the relationship which gives the horizontal component to the right, as illustrated in H6. 8. The upper view in FIG. 8 shows the position of the eccentrics at the end of the compacting action. The second and third views show the relation of the eccentrics as they exert their lifting action and their horizontal component of force to the right and the lower view shows the beginning of the compacting action which reaches its maximum when the eccentrics again reach the position shown in the upper view.

In describing the preferred embodiment, reference has been made to two eccentric weights on each shaft but it will be apparent to those skilled in the art that any number of eccentric weights from one up can be used and where the term eccentric or eccentric weight" is used in the claims, it will be understood to refer, un-

, less otherwise limited, to any suitable number of eccentric weights. Other modifications and variations within the principles of the invention as described will be obvi-- ous to those skilled in the art and such are contemplated by the following claims:

I claim:

1. A vibrator comprising:

a. a housing;

b. a driving shaft journaled in bearings supported by said housing having a driving gear and an eccentric weight thereon;

c. a driven shaft journaled in bearings supported by said housing in horizontal spaced relation from said driving shaft having a driven gear and an eccentric weight thereon;

d. means providing an operative connection between said gears to drive them and the eccentrics mounted on the shaft with them in opposite directions at the same speed to produce a force having vertical and horizontal components;

e. shift means for changing the angular relation of the eccentric weight on one of said shafts with respect to the eccentric weight on the other of said shafts to change the direction of the horizontal component of force; and

f. means outside of said housing for operating said shift means while the shafts are rotating comprising a pivoted lever, a kick plate on said lever at each side of said pivot in position to be engaged by the foot of an operator to reverse at will the direction of the horizontal component of force by kicking said plates alternately.

2. A self propelled reversible tamper comprising:

a. a housing;

b. a driving shaft joumaled in bearings supported by said housing having an eccentric weight thereon;

c. a driven shaft journaled in bearings supported by said housing having an eccentric weight thereon;

d. a gear on each shaft for rotating said shafts in opposite directions at the same speed;

e. means for making fixed connections of the eccentric weight on one of said shafts to the gear on its shaft in a single angular relation thereto;

f. means for making selective connection of the eccentric weight on the other of said shafts to the gear on its shaft in a plurality of different angular relations thereto;

g. a base plate to which said housing is secured;

h. a motor mounted on said base plate to drive said driving shaft; and

i. means including a kick plate outside said housing at each end of the tamper for changing said selective connection from one angular relation to another.

3. A self propelled reversible tamper as set forth in claim 2 in which a handle is secured to the base plate for operating the tamper from each end.

4. A self propelled reversible tamper comprising a base plate and a vibrator mounted thereon including a driving shaft having a driving gear and an eccentric mounted thereon for rotation therewith; a driven shaft having an eccentric and a driven gear mountedthereon, said eccentric being selectively adjustable to at least two different relative angular relations to each other; and external means at opposite ends of said tamper for selectively adjusting the angular relations of said eccentrics while the parts are rotating.

5. A self propelled reversible tamper as set forth in claim 4 in which said means for selectively adjusting said angular relations includes a kick plate at each of said opposite ends.

6. A self propelled reversible tamper as set forth in claim 4 which has a handle pivoted to said tamper for movement through an are from an operating position at one end to an operating position at the opposite end of said base plate.

7. A self propelled reversible tamper comprising:

a. a base plate having upturned ends;

b. a vibrator mounted on said base plate to provide vertical and horizontal components of force;

c. means for reversing the direction of said horizontal components of force;

d. a handle pivoted to said tamper for movement through an are from an operating position at one end to an operating position at the opposite end 'of said base plate; and

e. a kick plate independent of said handle at each end of said tamper for operating said means.

8. A self propelled reversible tamper comprising:

a. a base plate having upturned ends;

b. a vibrator for said base plate comprising:

1. a housing secured to said base plate;

2. a driving shaft journaled in bearings supported by said housing having an eccentric weight thereon;

3. a driving gear fastened to said driving shaft;

4. a driven shaft journaled in bearings supported by said housing having an eccentric weight thereon;

5. a driven gear mounted on said driven shaft;

6. means for making an adjustable driving connection through said driving and driven gears to the eccentric weight on said driven shaft to fix it in and kick plates are provided at each end of said tamper.

10. A tamper as set forth in claim 9 in which a handle is provided for operating the tamper from each end.

11. A tamper as set forth in claim 8 in which a handle is pivoted to said tamper for movement through an arc from an operating position at one end to an operating position at the other end of said base plate.

Claims

1. A vibrator comprising: a. a housing; b. a driving shaft journaled in bearings supported by said housing having a driving gear and an eccentric weight thereon; c. a driven shaft journaled in bearings supported by said housing in horizontal spaced relation from said driving shaft having a driven gear and an eccentric weight thereon; d. means providing an operative connection between said gears to drive them and the eccentrics mounted on the shaft with them in opposite directions at the same speed to produce a force having vertical and horizontal components; e. shift means for changing the angular relation of the eccentric weight on one of said shafts with respect to the eccentric weight on the other of said shafts to change the direction of the horizontal component of force; and f. means outside of said housing for operating said shift means while the shafts are rotating comprising a pivoted lever, a kick plate on said lever at each side of said pivot in position to be engaged by the foot of an operator to reverse at will the direction of the horizontal component of force by kicking said plates alternately.

2. A self propelled reversible tamper comprising: a. a housing; b. a driving shaft journaled in bearings supported by said housing having an eccentric weight thereon; c. a driven shaft journaled in bearings supported by said housing having an eccentric weight thereon; d. a gear on each shaft for rotating said shafts in opposite directions at the same speed; e. means for making fixed connections of the eccentric weight on one of said shafts to the gear on its shaft in a single angular relation thereto; f. means for making selective connection of the eccentric weight on the other of said shafts to the gear on its shaft in a plurality of different angular relations thereto; g. a base plate to which said housing is secured; h. a motor mounted on said base plate to drive said driving shaft; and i. means including a kick plate outside said housing at each end of the tamper for changing said selective connection from one angular relation to another.

3. a driving gear fastened to said driving shaft;

4. A self propelled reversible tamper comprising a base plate and a vibrator mounted thereon including a driving shaft having a driving gear and an eccentric mounted thereon for rotation therewith; a driven shaft having an eccentric and a driven gear mounted thereon, said eccentric being selectively adjustable to at least two different relative angular relations to each other; and external means at opposite ends of said tamper for selectively adjusting the angular relations of said eccentrics while the parts are rotating.

5. a driven gear mounted on said driven shaft;

6. A self propelled reversible tamper as set forth in claim 4 which has a handle pivoted to said tamper for movement through an arc from an operating position at one end to an operating position at the opposite end of said base plate.

6. means for making an adjustable driving connection through said driving and driven gears to the eccentric weight on said driven shaft to fix it in a plurality of different angular relations to the eccentric weight on said driving shaft;

7. an external pivoted shift lever including a kick plate at each side of said pivot in position to be engaged by the foot of an operator for selectively adjusting said means to each such fixed relation, and c. means for rotating said driving shaft.

7. A self propelled reversible tamper comprising: a. a base plate having upturned ends; b. a vibrator mounted on said base plate to provide vertical and horizontal components of force; c. means for reversing the direction of said horizontal components of force; d. a handle pivoted to said tamper for movement through an arc from an operating position at one end to an operating position at the opposite end of said base plate; and e. a kick plate independent of said handle at each end of said tamper for operating said means.

8. A self propelled reversible tamper comprising: a. a base plate having upturned ends; b. a vibrator for said base plate comprising:

9. A tamper as set forth in claim 8 in which a lever and kick plates are provided at each end of said tamper.