Patent Application
20210040700
The present invention relates to a rammer.
Patent Document discloses a conventional rammer which includes an engine, a reciprocating mechanism to convert a rotational force of the engine into a reciprocal force, a leg part disposed to lean forward in a moving direction and being moved up and down by the reciprocating mechanism, and a compacting plate disposed at an bottom of the leg part.
The reciprocating mechanism includes a crank mechanism where a pinion gear of an output shaft of the engine is engaged with a crank gear of a crank shaft. The crank gear is provided with a crank pin at a position offset from the rotational axis of the crank shaft, and a connecting rod is connected to the crank pin. The crank shaft is disposed in a front-rear direction (strictly speaking, inclined forward and downward in the front-rear direction of a rammer body), and a connecting rod rotates while being repeatedly displaced in a right-left direction of the rammer body.
Patent Document 1: Japanese Patent Application Publication No. JPH11-140815
According to the technique of the Patent Document 1, the connecting rod is displaced in a right-left direction of the rammer body, and the rammer body also sways in the right-left direction, to have a risk of being unstable.
The present invention is intended to provide a rammer having excellent stability in the position of the rammer body to address such a problem.
To solve the problem, the present invention provides a rammer including: an engine; a reciprocating mechanism including a crank shaft and a connecting rod and configured to convert a rotational force of the engine into a reciprocal force; a leg part disposed to lean forward in a moving direction and configured to be moved up and down by the connecting rod; and a compacting plate disposed at a bottom of the leg part. The leg part includes: an outer cylinder; an inner cylinder slidably contacted with an inside of the outer cylinder; a slider connected to the connecting rod and slidably provided in the inner cylinder; a first coil spring housed in an upper part of the inner cylinder; and a second coil spring housed in a lower part of the inner cylinder. The slider is disposed between the first coil spring and the second coil spring. The crank shaft has a rotational axis disposed orthogonally to the moving direction. The first coil spring and the second coil spring have respectively different winding directions to each other.
According to the present invention, the connecting rod is displaced in a front-rear direction of the rammer, and swaying of the rammer in a right-left direction is reduced when the rammer moves forward, and a gyro effect allows the rammer to stably jump forward. The first coil spring and the second coil spring have respectively different winding directions to each other, and thus twisted forces from the springs cancel each other out to further improve stability of the rammer.
The present invention also has a feature that a thrust bearing is provided on at least one of an end of the first coil spring and an end of the second coil spring.
In the present invention, the thrust bearing absorbs the twisted force generated by expanding and contracting of the springs and thus further reduces the twisted force impacting on the rammer body.
In the present invention, the connecting rod is displaced in a front-rear direction of the rammer, to have swaying of the rammer in a right-left direction reduced while the rammer moves forward, and the gyro effect improves stability of forward movement of the rammer. The first coil spring and the second coil spring have respectively different winding directions to each other, and thus the twisted forces from the springs cancel each other out to further improve stability of the rammer.
A rammer 1, as shown in
The handle 7, as shown in
The engine 2 is a gasoline engine for example. The engine 2 includes an output shaft 9 (see
The reciprocating mechanism 3, as shown in
The belt deceleration mechanism 16 includes: a driving pulley 18 axially attached on the output shaft 9 of the engine 2 (see
In
The crank shaft 13 is disposed behind the gear shaft 21 with the rotational axis of the crank shaft 13 set in the right-left direction orthogonal to the moving direction of the rammer 1. Both ends of the crank shaft 13 are axially supported by the case 4 via a bearing 26. The large diameter gear 25 is axially attached to the crank shaft 13 at a portion close to the right end of the crank shaft 13. The crank shaft 13 is formed with a crank pin 27, which is being offset from the rotational axis of the crank shaft 13, at the center in the axial direction. The crank pin 27 is connected to the upper part of the connecting rod 14 via a bush 28. The lower part of the connecting rod 14, as shown in
The leg part 5, as shown in
The outer cylinder 31 has a cylindrical shape having upper and lower ends thereof opened. The piston 36 is slidably housed inside the outer cylinder 31 and has a sliding part 36A connected to the connecting rod 14 and sliding in the upper part of the outer cylinder 31 and also has a coupling rod 36B extending downward from the sliding part 36A. The lower end of coupling rod 36B is provided with a male screw 36C threaded downward. An upper flange 5A is fixed on the outer circumference of the upper part of the outer cylinder 31 by welding or the like. The upper flange 5A, as mentioned above, is fastened with the bolts 11 and the nuts 12 to the lower flange 4A of the case 4. The plate member 10 is sandwiched between the upper flange 5A and the lower flange 4A. Accordingly, the outer cylinder 31 is fixed integrally to the case 4 with the bolts 11 and the nuts 12.
The inner cylinder 32 has the upper side inserted in the outer cylinder 31 from the opening part at the lower end of the outer cylinder 31 and contact with an inside of the outer cylinder 31. A spring-supporting plate 32A is formed at the upper end of the inner cylinder 32. A through hole 32C, which the coupling rod 36B of the piston 36 passes through, is formed at the center of the spring-supporting plate 32A. A flange 32B is formed on the outer circumference of the lower end of the inner cylinder 32. The upper end of the compacting plate 6 is provided integrally with a leg base 37. The flange 32B of the inner cylinder 32 is fastened to the leg base 37 with bolts 38.
A cylindrical leg cover 39 is arranged on the outer side of the inner cylinder 32 and fastened together with the inner cylinder 32 with the bolts 38. A waved bellows 40 is disposed between the leg cover 39 and the upper flange 5A. The bellows 40 is made of a rubber or the like and couples the outer cylinder 31 with the inner cylinder 32 to support a sliding movement between them.
The slider 33 is a circular plate member which has an outer surface sliding on the inner surface of the inner cylinder 32. The slider 33 is fastened and fixed to the lower end of the coupling rod 36B of the piston 36 with a nut 41 and a male screw 36C passing through a through hole of the slider 33. The upper part of the slider 33 and the upper part of the leg base 37 are provided with stoppers 42 and 43, respectively. The stoppers 42 and 43 contact the spring-supporting plate 32A and the nut 41 when excessive vibration occurs, to regulate stroke of the inner cylinder 32. The stopper 42 and 43 also serve to reduce a position deviation of a first inner coil spring 34B and a second inner coil spring 35B to be described below.
In the present embodiment, the first coil spring 34 includes a first outer coil spring 34A having a larger diameter and a first inner coil spring 34B having a smaller diameter arranged inside the first outer coiled spring 34A. The first outer coil spring 34A and the first inner coil spring 34B have respectively different winding directions to each other to prevent each spring from engaging with each other, such that, when the first outer coil spring 34A is right-handed, the first inner coil spring 34B is left-handed. The first outer coil spring 34A and the first inner coil spring 34B have upper ends thereof supported by the spring-supporting plate part 32A and have lower ends thereof supported by the slider 33 and housed in a compressed state in the inner cylinder 32.
A second coil spring 35 also includes a second outer coil spring 35A having a larger diameter and a second inner coil spring 35B having a smaller diameter and arranged inside the second outer coil spring 35A. The second outer coil spring 35A and the second inner coil spring 35B have respectively different winding directions to each other not to engage with each other. The second outer coil spring 35A and the second inner coil spring 35B have upper ends thereof supported by the slider 33 and have lower ends thereof supported by the leg base 37 and housed in a compressed state in the inner cylinder 32.
The first coil spring 34 and the second coil spring 35 have respectively different winding directions to each other and are housed in the inner cylinder 32. When a rammer has an outer coil spring and an inner coil spring as in the present embodiment, in regard to a relationship between the outer coil springs, that is, in regard to a relationship between the first outer coil spring 34A and the second outer coil spring 35A, they have respectively different winding directions to each other. Likewise, in regard to a relation between the inner coil springs, that is, in regard to a relationship between the first inner coil spring 34B and the second inner coil spring 35B, they also have respectively different winding directions to each other.
Thrust bearings 44 are provided between the lower end of the first coil spring 34 and the slider 33 and between the upper end of the second coil spring 35 and the slider 33, respectively. Respective thrust bearings 44 are housed in corresponding bearing housing parts 45 annularly recessed near outer circumferences of both the upper and lower surfaces of the slider 33. Each thrust bearing 44 includes needle bearing, roller bearing, or ball bearing. Washers 46 are in plane contact against the first coil spring 34 and the second coil spring 35 respectively and inserted between the first coil spring 34 and the thrust bearing 44 and between the second coil spring 35 and the thrust bearing 44 respectively. Each washer 46 is formed to have a lager thickness at a portion close to the outer edge than at the rest to prevent the washer 46 from inclining and loosely fitted in a bearing housing part 45.
When the output shaft 9 of the engine 2 rotates, the gear shaft 21 rotates while being decelerated by the belt deceleration mechanism 16, and then the crank shaft 13 rotates while being decelerated by the gear deceleration mechanism 17. A crank movement of the connecting rod 14 results in an up-down movement of the slider 33, so that the first coil spring 34 and the second coil spring 35 expand and contract to move the inner cylinder 32 up and down relative to the outer cylinder 31. Thereby, the compacting plate 6 firmly compacts a ground.
The present invention has following advantageous effects. (1) The crank shaft 13 is disposed such that the rotational axis of the crank shaft 13 is set in a right-left direction, or an orthogonal direction to the moving direction of the rammer 1. This causes the connecting rod 14 to be displaced in the front-rear direction of the rammer 1 to reduce swaying of the rammer 1 in a right-left direction when moving forward, and to allow the rammer 1 to stably jump forward by the gyro effect.
(2) The first outer coil spring 34A and the second outer coil spring 35A have respectively different winding directions to each other. Thus, the resilient force of the first outer coil spring 34A generates a force moment on the spring-supporting plate 32A in one direction around a cylinder axis O of the cylinder mechanism 30, and the resilient force of the second outer coil spring 35A generates a force moment on the leg base 37 in the other direction around the cylinder axis O. Thus, the force moment generated on the spring-supporting plate 32A and the force moment generated on the leg base 37 cancel each other out, to reduce a twisting of the inner cylinder 32. Also on the slider 33, the resilient force of the first outer coil spring 34A generates a force moment in one direction around the cylinder axis O and the resilient force of the second outer coil spring 35A generates a force moment in the other direction around the cylinder axis O. Both force moments cancel each other out, to reduce the twisting of the slider 33. This reduces unstable portion of the rammer 1 due to the twisting. Advantageous effects between the first inner coil spring 34B and the second inner coil spring 35B are the same.
The thrust bearing 44 is provided at least one of the end part of the first coil spring 34 and the end part of the second coil spring 35, to have following advantageous effects. Twisted forces act on supporting parts for the four end parts which are both end parts of the first coil spring 34 and both end parts of the second coil spring 35. At least one of the end parts is provided with the thrust bearing 44 and this helps absorb the twisted force generated by expanding and contracting of the spring and thus further reduces the impact on a rammer body. The thrust bearing 44 may preferably be provided on both the upper and lower surfaces of the slider 33, as in the present embodiment, because the bearing housing parts 45 are formed in the slider 33 easily. Alternatively, the thrust bearing 44 may be provided in some cases between the upper end of the first coil spring 34 and the spring-supporting plate 32A or between the lower end of the second coil spring 35 and the leg base 37.
As can be seen by a comparison of
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-047739 | Mar 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/006609 | 2/21/2019 | WO | 00 |
