Percussion Device

Abstract

A lightweight percussion device operating from a motor driven crank which reciprocates a hollow inner cylinder closed at both ends and slidably mounted in an outer cylinder with a piston having a rod extending through one end of the inner cylinder and slidably mounted in the inner cylinder; a set of ports are provided adjacent each end of the inner cylinder and spaced from the adjacent end of the inner cylinder and one set of ports spaced from the other ports a distance in the order of the throw of the crank with the ports communicating with the atmosphere so that rotation of the crank causes reciprocation of the inner cylinder and the confined gas between the end of the piston and the adjacent end of the inner movable cylinder causes the piston to reciprocate while the piston is cushioned at each end of its movements and the rod projecting from the piston serves to produce a hammering action on a gad or other tool.

Description

The present invention relates to a machine for chipping operations, such as the crushing of concrete blocks and rocks, the driving of piles and nails and the removal of fins and shells from the face of cast metal and the outer hull plate of a ship or any other operation that is generally conducted by percussion forces.

Air hammers actuated by compressed air have been used for this purpose but have required large air compressors and long pipes leading to the air hammer.

Other systems have used the explosive forces of ignited gases and some have used a vacuum system with a small hole in the piston which used the vacuum to raise the piston until the vacuum chamber was filled with air and the piston caused to strike a gad or other suitable tool. These various systems required complicated mechanisms and were difficult to maintain and were cumbersome in use and the prior air hammers have been excessively heavy requiring substantial effort to maintain the air hammers in position of use.

An object of the present invention is to provide a percussion device which overcomes the difficulties of the prior art air hammers.

Another object of the present invention is to provide a percussion device operating from a small rotatory motive power.

A further object is to provide a percussion device of light weight which is efficient in use reducing the cost of performing useful work.

Other and further objects will be apparent as the description proceeds and upon reference to the accompanying drawings; wherein:

FIG. 1 is a longitudinal sectional view taken transverse to the crank axis;

FIG. 2 is a longitudinal section of the device with the section taken substantially parallel with the crank axis and with part broken away to show the structure of the crank discs;

FIG. 3 diagrammatically illustrates the cycles of operation.

The percussion device includes a casing 6 having a handle 6a at the upper end thereof with pinion gears 1 rotatably mounted in suitable bearings and driving disc gears 2 mounted in suitable bearings with the disc gears including counterweights 3 having window openings 4 adjacent the crank pin 5 extending between the disc gears. The pinion gears 1 are driven from a shaft 7A suitably mounted in a bearing 7 and which shaft 7A is driven from a suitable source of rotary power such as an electric motor or an internal combustion engine.

Mounted on the gear casing 6 is an outer cylinder which includes an outer sleeve 8 and an inner sleeve 8A spaced from the outer sleeve by spacing sleeves 8B and 8C adjacent each end leaving an open space 17 between the outer sleeve 8 and the inner sleeve 8A of the outer cylinder.

Slidably mounted in the inner sleeve 8A is an inner cylinder 9 closed at one end by a removable threaded closure 10 and closed at the other end by end wall 11 a which end wall 11 has an opening through which a rod 15 reciprocates with the rod 15 fixed to or being a part of piston 14 slidably mounted within the bore of the inner cylinder 9 and such inner cylinder is reciprocated from the crank pin 5 by means of the connecting rod 12. The ends of the inner cylinder have a larger diameter than the intermediate portion thereby leaving an open space 13 between the periphery of the intermediate portion of the inner cylinder and the sleeve 8A of the outer cylinder. Ports 16 in the periphery of the inner cylinder adjacent the end 11 provide for air to enter the space between the bottom of the piston 14 and the lower end wall 11 while similar ports 16' adjacent the end 10 provide for the passage of air into the space between the upper end of the piston 14 and the closed end 10 and also provide for communication with atmospheric air through the space 13 and through the ports 11c to the space 17 between the sleeves 8A and 8, other ports 11a and 11b are provided adjacent the tope and bottom of the sleeve 8A and suitable openings, not shown, are provided to the exterior so that the inner cylinder 9 can move freely.

An end bushing 18 is secured to the lower end of the outer cylinder by any suitable means and has a bore therethrough which receives the head of a tool such as a gad 19 which is held in operative relation in the bushing 18 by a U-shaped plate 20 which embraces the gad 19 below a stop flange 19A which abuts a boss on the bushing 18 when the gad is in proper position so that the head of the gad will be struck by the had hammering hammering rod 15 of the piston. The U-shaped plate 20 is held in gad retaining position by springs 21 reacting against lugs 21A through which the bolts 21B pass with the springs 21 surrounding the bolts 21B and being adjustable by means of the nuts 21C, it being apparent that the arrangement provides for insertion and removal of the gad 19 when desired.

Referring to the diagrammatic illustrations in FIG. 3 and beginning with the diagram I the crank pin is shown in its lowered position and the inner cylinder in its lowered position with hammer rod 15 engaging the head of the gad 19 with the piston shown in its upper position leaving a space d and in this position the ports 16 provide communication to the space d as shown in FIG. 1 and the upper end of the piston is closely adjacent the top 10 of the inner cylinder 9 with a clearance y.

Assuming the direction of rotation shown by the arrow the crank pin moves to the position II thereby moving the inner cylinder 9 upwardly a distance d so that the upper space communicates through the ports 16' to the atmosphere while the gas between the bottom of the piston 14 and the closure 11 is reduced to the distance y thereby compressing the gas and exerting a force on the piston 14 which raises the piston upwardly as the crank 5 moves to position III and the inertia of the piston causes the piston to continue to move upwardly while the crank 5 moves to the position IV thereby compressing the gas in the upper end to an amount y and the high pressure of such gas causes the piston 14 to move downwardly as the crank 5 moves to its bottom dead center position whereby the piston 14 is caused to move so that the hammer rod 15 contacts the head of the gad 19 producing the hammering effect and the steps are repeated so that a hammering blow occurs upon each revolution of the crank 5; illustrations V and VI are similar to illustrations I and II showing that the cycles are repeated.

It will be noted that the force on the crank pin is substantially cushioned by the confined air under pressure at both ends of the piston 14 and both ends of the inner cylinder 9 so that there is no danger of impact of the piston against the ends 10 and 11 of the inner cylinder 9. It will also be noted that the ports 16 and 16' provide for the entrance of air into the end spaces d while the air pressure in the end spaces y increases to provide the necessary cushioning and the necessary driving force for the piston 14. The air is provided from the atmosphere and the arrangement of the ports is such as to minimize mechanical losses an minimize interference with the operation of the percussion device.

The inner cylinder 9 is of very lightweight since it does not directly impact the gad 19 and therefore the forces on the crank pin and the bearings is kept to a minimum while the piston 14 which does strike the gad 19 through the hammer rod 15 can be made heavy and the kinetic energy produced by the downward movement of the piston produces the hammering action on the gad and therefore the piston can be made very heavy without directly affecting the cylinder 19 and the bearings and the compressed air gradually produces the buffer effect and prevents the piston from striking the ends 10 and 11 of the lightweight cylinder 9.

It has been found by experiments that when the space d between the lower surface of the piston 14 as shown in FIG. 3-I is arranged so that the inner surface of the bottom of inner cylinder 9 is approximately the same as the radius from the axis o to the crank pin 5 and the ports 16 are in proper position to admit air that the device works well and similarly when the ports 16' are arranged a similar distance from the upper end of the cylinder 9 the combination with this arrangement has been found very satisfactory.

If it is attempted to get a very long stroke of the piston 14 in the inner cylinder the operation has not been entirely satisfactory and consequently the arrangement of the ports and the length of the cylinder 9 with respect to the length of the piston 14 is adjusted to obtain the desired operation so that a hammering action occurs for each rotation of the crank pin 5.

The window holes or openings 4 in the counterbalancing weights 3 provide for mitigating the shock that the rebound gives to the operator when the gad 19 receives its hammering stroke and the arrangement of the window holes with respect to the crank are shown in the illustrations I through VI of FIG. 3 and it has been found that the weight of the percussion device of the present invention can be reduced to approximately 20 kilograms whereas the weights of the well known compressed air type of air hammer must be as heavy as 40 to 50 kilograms and this saving in weight with the increased efficiency of the present invention provides for smooth and effective operation with a minimum of effort.

In the ordinary air hammer pressures of approximately 7 atmospheres are used while with the present invention the pressure in the end y of the cylinder 9 can be 20 to 25 atmospheres or higher and therefore the force on the piston can be very great.

Since the piston 14 is fitted in the cylinder 9 for free movement there is no danger of one-sided abrasion on the sliding surface of the cylinder 9 or the piston 14 resulting in less wear and even though some wear does occur the present invention can be used for a long period of time without requiring expensive maintenance.

Since the air pressure reacts on the piston 14, the impact shock of the piston 14 on the gad is not directly taken by the crank 5 making high speed work possible with a small size motor of small horsepower.

Since the cog wheel discs 2 and the balance wheels 3 supporting the eccentric pin have the window holes 4 the center of gravity of the balance wheels is opposite to the crank pin 5 neutralizing the rebound of the crashing shock against the gad 19 so that crushing work can be performed by a device of extremely light weight.

The percussion device of the present invention may be operated by a motor of 2 or 3 horsepower and even though the entire weight is only 20 kg. it can penetrate through a concrete block of 30 cm. thick in 5 seconds.

It will be apparent that changes may be made within the spirit of the invention as defined by the valid scope of the claims.

Claims

I claim:

1. A percussion device comprising an outer cylinder, a crank mounted on said outer cylinder, a small rotary motor power means to rotate said crank, an inner hollow cylinder having closed ends slidably mounted in said outer cylinder and operatively connected to said crank whereby when said crank rotates said inner cylinder reciprocates, a piston mounted for reciprocation in said inner cylinder, a rod extending from said piston through an end wall of said inner cylinder, said inner cylinder having ports spaced from the ends whereby rotation of said crank causes reciprocation of said inner cylinder and thereby reciprocation of said piston by the force of compressed gas confined in the alternately closed ends of the hollow inner cylinder, the rod of said piston being adapted to impact a tool producing a hammering action on the tool, the crank radius being approximately the same as the distance from the end of the inner cylinder to the adjacent ports, the inner cylinder having a reduced outside diameter intermediate the ends and the ports are located in this reduced diameter portion, and the length of the piston is substantially equal to the distance between one end and the ports adjacent the other end of the inner cylinder.

2. The invention according to claim 1 in which the outer cylinder includes an outer and inner sleeve with clearance between the sleeves and are provided intermediate and at both ends in the inner sleeve to the ambient air.

3. The invention according to claim 2 in which the openings in the inner sleeve are located adjacent each end and adjacent the midportion.