US3468383A

US3468383A - Control of air supply for pneumatic impact hammers

Info

Publication number: US3468383A
Application number: US715275A
Authority: US
Inventors: Eimatsu Kotone
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-03-22
Filing date: 1968-03-22
Publication date: 1969-09-23
Anticipated expiration: 1986-09-23

Description

Sept. 23, 1969 EIMATSU KOTONE CONTROL OF AIR SUPPLY FOR PNEUMATIC IMPACT HAMMERS Filed March 22, 1968 3 Sheets-Sheet 1 G 8 r r R 2 o l E I W w v N L L A 6 v R H O L 5 7 .V m \1 R 7 m 4R M w A S H E On P M o C INVENTOR EIMATSU KOTONE ATTORNEYS HAMMER 6O COMPRESSOR RESERVOIR FIGB p 23, 1969 EIMATSU KOTONE 3,468,383

I CONTROL OF AIR SUPPLY FOR PNEUMATIC IMPACT HAMMERS Filed March 22, 1968 3 Shuts-Sheet g EIMATSU KOTONE ATTORNEYS Sept 1969 EIMATSU KOTONE 3,468,383

CONTROL OF AIR SUPPLY FOR PNEUMATIC IMPACT HAMMERS Filed March 22, 1968 3 Sheets-Sheet :5

COM PPESSOR SSE FIG]

INVENT OR E IMATSU KOTONE ATTORNEYS United States Patent 3,468,383 CONTROL OF AIR SUPPLY FOR PNEUMATIC IMPACT HAMMERS Eimatsu Kotone, 4 Aza-Nishiyama 193, Kobayashi, Takarazuka-shi, Hyoga-ken, Japan Filed Mar. 22, 1968, Ser. No. 715,275 Int. Cl. B23q /00; Bd 9/14; B2lj 7/24 U.S. C]. 173-1 6 Claims ABSTRACT OF THE DISCLOSURE Method for controlling the supply of air from an air compressor to a pneumatic impact hammer by way of an air reservoir by intermitting, decreasing, or bypassing the flow intermediate the reservoir and the hammer piston to suspend the reciprocations of piston intermittently, to retard the piston during the return stroke, or to cause a time lag prior to the return stroke of the piston, so as to provide continuous alternation of an air consuming cycle and an air saving cycle for the compressed air during the operation of the hammer.

The present invention relates to improved method for controlling air fiow, and in its more particular aspects it has to do with the application of these methods to pneumatic impact hammers of a kind which, in connection with a compressed air source of the continuous supply type, automatically reciprocates a piston against a tool and applies a repeated impact to an object with which the tool is in contact.

Pneumatic impact hammers are commonly used to crush concrete aggregates for construction material and to drive piles at construction sites. An increase in the required impact power of a pneumatic impact hammer will ordinarily require a corresponding increase in the supply capacity of the air compressor used as the source of compressed air resulting in quite an increase in the overall purchase price of a hammer accompanied by a compressor. It is therefore desired to provide, by improved methods of controlling the supply system, a way in which the hammer can exert powerful impacts while using an air compressor of comparatively small capacity as a compressed air source.

The general method of the present invention involves regulation of the air supply in which compressed air flow is controlled intermediate the supply end and the consuming end in a manner to accumulate pneumatic pressure from the compressed air supplied at the supply end which is sufficient for the required impact value at the consuming end.

A method such as generally described above is widely known, but has not been improved sufliciently for application to pneumatic impact hammers of the above-described kind for the purpose of exerting very powerful impacts from a compressed air source of comparatively small continuous supply capacity. The pneumatic impact hammers of this kind generally have a cylinder provided with a plurality of ports to supply and discharge compressed air, a tool holder axially secured to the lower end of the cylinder, a tool supported in the tool holder and slidably guided therein so as to be in contact with the object and a piston reciprocable within the cylinder and carrying out alternate impact strokes and return strokes relative to the tool to apply repeated impacts to the object with which the tool is in contact. The supply port or ports are connected to an air compressor through an intermediate air reservoir provided on the delivery side of the compressor. It will therefore be understood in the description of the invention that the air reservoir represents the compressed air supply end while the hammer piston represents the consuming end.

ice

A principal object of the invention is to provide improved methods to enable a pneumatic impact hammer to exert powerful impacts while using an air compressor of comparatively small capacity as a compressed air source.

A more specific object of the invention is to regulate compressed air flow from the reservoir of an air compressor to the piston of a pneumatic impact hammer in a manner such that the reciprocations of the piston are suspended intermittently so as to enable build up of compressed air in the reservoir during the suspension sufliciently to enable supplying an amount of air sufiicient for the resumption of the reciprocations of the piston following the suspension of reciprocations.

Another specific object of the invention is to regulate compressed air flow from the reservoir of an air compressor to the piston of a pneumatic impact hammer in a manner to retard each return stroke of the piston so as to enable build up of compressed air in the reservoir during the retardation sufiiciently to enable supplying an amount of air sufiicient for the resumption of the impact stroke of the piston following the retarded return stroke.

Still another specific object of the invention is to regulate compressed air flow from the reservoir of an air compressor to the piston of a pneumatic impact hammer in a manner to provide a time lag from the end of each impact stroke to the beginning of the successive return stroke of the piston so as to enable build up of compressed air in the reservoir during the time lag sufiiciently to enable supplying an amount of air suflicient for the resumption of the reciprocation of the piston following the time lag.

Other objects and various features of the invention will be more apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagramatic view of a pneumatic system which can be used to carry out the principle of the invention;

FIG. 2 is an enlarged sectional view of the regulating valve used in the pneumatic system show in FIG. 1;

FIG. 3 is a diagrammatic view of a modification of the pneumatic system of FIG. 1, with the regulating valve on an enlarged scale and shown in section;

FIG. 4 is a circuit diagram of a circuit for controlling the pneumatic system shown in FIG. 3;

FIG. 5 is a diagrammatic view, including the cylinder of an impact hammer on an enlarged scale and in vertical section, of another pneumatic system which can be used to carry out the principle of the invention;

FIG. 6 is an enlarged sectional elevation of the regulating valve used in the pneumatic system in FIG. 5; and

FIG. 7 is a diagrammatic view, in elevation of still another pneumatic system which can be used to carry out the principle of the invention.

If an air compressor has a small rated capacity relative to the compressed air requirements necessary to provide the desired impact power of the hammer to which it supplies compressed air through an air reservoir, repetition of impact by the hammer will continuously decrease the pneumatic pressure in the reservoir until finally it falls short of the minimum value necessary for the hammer to exert impacts at the piston end with the required force. It will then be necessary for maintaining the impact force at the required value that the decrease of pneumatic pressure in the reservoir be stopped and instead be increased before it reaches the minimum value for maintaining the impact force of the hammer. In other words, it will be necessary that for one period of time compressed air be accumulated in the reservoir while for another period of time it will be consumed at the piston end of the hammer, so that there will never be a deficiency in the amount required for consumption at the piston end. In still other words, it will be necessary to provide a consuming cycle and an accumulation cycle for the compressed air which are repeated alternately in the automatic operation of the impact hammer, so that the required impact force will always be produced at the piston end during the consuming cycle. The consuming cycle will follow the accumulation cycle during which sufficient compressed air is accumulated in the air reservoir for the supply capacity of the air compressor.

Theoretically there could be several various methods to provide such a consuming cycle and an accumulation cycle for the automatic operation of pneumatic impact hammers, but three of them will be most practical; one is the intermittent suspension of the operation of the hammer, another is the retardation of the return, and the third is a time-lag return. The present invention is particularly related to these three methods. The intermittent suspension method in principle involves intermitting the compressed air flow intermediate the air reservoir and the hammer piston to stop or suspend the reciprocations of the piston intermittently so as to provide an accumulation time for the compressed air corresponding to the time during which reciprocations are suspended and a consuming cycle corresponding to the time over which there occurs resumption of the reciprocations of the piston. The method involving retardation of the return is in principle to decrease the flow of compressed air intermediate the air reservoir and the hammer piston to retard or slow down each return stroke of the piston so as to provide time for accumulation of compressed air corresponding with the retarded return stroke and a consuming cycle corresponding with the impact stroke of the piston following the retarded return stroke. The time-lag return method is in principle to bypass the compressed air EfiOW intermediate the air reservoir and the hammer piston to cause or.provide a time-lag from the end of each im pact stroke to the beginning of the successive return stroke of the piston so as to provide a time for accumulation of compressed air corresponding to the time-lag and a consuming cycle corresponding with the reciprocation of the piston following the time-lag.

The intermittent suspension method of the invention can be carried out in a practical manner by a pneumatic system such as is shown in FIG. 1. This pneumatic system primarily consists of an impact hammer 9, an air compressor 7 having the delivery side connected by a valved line 7 to an air reservoir 8 intermediate the hammer 9 and the compressor 7, and a pneumatic control type regulating valve 50 connected in line 11, 12 intermediate the reservoir 8 and the hammer 9. Control line 11' is connected between the reservoir 8 and the control port of the valve 50-.

The regulating valve 50 comprises a casing 50 having a pair of axial apertures 1 and 48 and a pair of radial apertures and 5, a valve member 6 slidably enclosed in the casing 50' and having a fine axial bore 47 therethrough. The valve member has a full diameter part 6a and a reduced diameter part 6b. A head 2 is afiixed to one end of valve member 6 and is guided slidably in the axial aperture 1, and a spring 3 is compressed between the other end of valve member 6 and the end of casing 50' urges valve member 6 to the right in FIG. 2. The radial apertures 5 and 5' are located diametrically opposite each other. The pipes 11, 11 and 12 are joined to the

apertures

5, 1 and 5, respectively.

Considering the practical operation of such a pneumatic system to carry out the intermittent suspension method according to th! invention, and referring to FIGS. 1 and 2, the regulating valve 50 initially has the valve member 6 in the right most position due to the force of spring 3 as shown in full lines in FIG. 2, thereby causing part 6a to block communication between the apertures 5 and 5', and blocking the aperture 1 with the head 2, so that no air flows from the reservoir 8 to the impact hammer 4 9 when the compressor 7 delivers compressed air into the reservoir 8.

When pressure is increased to a given value in the reservoir 8. the valve member 6 with head 2 is driven to the left position against the force of spring 3 by the increased pressure applied to the head 2 through the pipe 11' until the valve member 6 reaches the position shown in dotted lines in FIG. 2. There is thus opened an air passage around reduced diameter part 6b between the apertures 5 and 5' to permit air to flow from the reservoir 8 to the hammer 9 while the compressor 7 continues to deliver compressed air into the reservoir 8. The air now supplied to the hammer drives the piston reciprocatively in the cylinder and supplies impacts repeatedly to the object contacted by the tool.

If the air compressor 7 has a small rated capacity relative to the requirements for impact of hammer 9 with the desired force, pressure is continuously decreased in the reservoir 8 as the hammer 9 repeats the impacts continuously due to the consumption of air at the hammer piston end.

When the pressure has decreased to a given value in the reservoir 8. the pressure on the right hand end of the valve member 6 with head 2 is reduced and the valve member is returned to the original right hand position by the expansion of spring 3, thereby again closing the air passage between the

apertures

5 and 5 and interrupting the air flow from the reservoir 8 to the hammer 9 and at the same time again blocking the aperture 1 with the head 2. While flow of compressed air is interrupted at the regulating valve 50, compressed air is not consumed at the piston end of hammer 9 at all, but is accumulated in the reservoir 8, and therefore the pressure is continuously increased in the reservoir 8 until it is raised again to a value sufiicient to drive the valve member 6 and head 2 to the left.

As long as compressed air is delivered continuously into the reservoir 8 from the compressor 7, the impact hammer 9 automatically repeats the above described alternation of a consuming cycle and an accumulation cycle, consuming compressed air and reciprocating the piston during the former cycle while leaving the piston at rest and accumulating compressed air during the latter cycle.

The bore 47 facilitates the movement of valve member 6. When the valve member 6 is moving to the left, the bore 47 releases a part of the relatively high pressure air to avoid abrupt movement of the valve member 6. When the valve member 6 is moving to the right, the bore 47 releases a part of the remaining air under pressure to assure quick return of the valve member 6. In either instance, the air released through the bore 47 is finally discharged into the atmosphere through the aperture 48.

The pressure sufficient to drive the valve member 6 to the left is the maximum pressure desired in the reservoir 8, while the pressure allowing the valve member 6 to return to the right is the minimum pressure desired in the reservoir 8. Accordingly in the reservoir 8, pressure continuously decreases from the maximum down to the minimum value during the consuming cycle, and continuously increases from the minimum up to the maximum during the accumulation cycle.

If the head 2 has as its largest cross sectional area 21rA and the valve member 6 has as its largest cross sectional area 2713, the pressure sufiicient to drive the valve member 6 to the left times 211'A is equal to or greater than the compressing force of spring 3, while the pressure to permit the valve member 6 to return to the right times 21B is less than the compression of spring 3, B being larger than A. It follows that the maximum pressure desired in the reservoir 8 is equal to B/A times the minimum pressure desired in the reservoir 8, B being larger than A. The minimum pressure desired in the reservoir 8 is necessarily the value suflicienl for the required impact force or hammer 9 at the piston end.

Since the minimum pressure in the reservoir Sis a value suflicient for the required impact force at the piston end, the hammer 9 always produces impacts of the required force to the object as long as the piston is reciprocated in the cylinder. Therefore, the intermittent suspension method of the invention makes it possible for the pneumatic impact hammer to exert powerful impacts even when supplied by an air compressor of comparatively small capacity.

The intermittent suspension method according to the invention can also be carried out by a pneumatic system such as is shown in FIG. 3. This pneumatic system comprises an impact hammer 57, an air compressor 55 connected to an air reservoir 56 provided on the delivery side of compressor 55 through a valved line 58, the reservoir being connected to the hammer 57 through a line 59 valved by a solenoid which actuates control valve 57'. A regulating valve 60 of the electric control type is connected to the reservoir 56 by pipe 66.

The regulating valve 60 which is combined with an electric circuit as shown in FIG. 4 for electric control of valve 57', comprises a casing 60' having a pair of

axial apertures

61 and 67, a valve member 65 slidable in the casing 60', .a valve rod 62 extending from the valve member 65 through aperture 61 and having a contact member 63 at the free end thereof, and a spring 64 bearing against one end of the valve member 65 to move it to the right. The pipe 66 is connected to the aperture 67.

The electric circuit combined with the valve 60 comprises a solenoid 54 to control the operation of the valve 57 to close and open the air line 59, a relay 53 having a holding contact 51 and a circuit closing contact 52 in the solenoid circuit to excite the solenoid 54 respectively, and a pair of

micro switches

68 and 69 to actuate the relay 53. These circuit elements are electrically connected as shown in FIG. 4.

In the operation of such a pneumatic system and referring to FIGS. 3 and 4 it will be seen that compressed air flow from the air reservoir to the impact hammer is intermitted under electric control, while in the previous example the compressed air flow is intermitted under pneumatic control. Initially, the regulating valve 60 has the valve member 65 in the rightward position under the force of spring 3, with the contact member 63 being in contact with and opening the micro switch 69. In this state, both the

micro switches

68 and 69 are opened, thus leaving the

relay contacts

51 and 52 opened, and therefore the relay 53 is not actuated and the solenoid 54 is not actuated. The valve 57 is closed to prevent air from flowing from the reservoir 56 to the hammer 57, while the compressor 55 runs to deliver cmpressed air into the reservoir 56.

When the pressure in the reservoir 56 is increased to a given value, the valve member 65 is driven to the left against the force of spring 64 by the increased pressure applied to its end surface through the pipe 66, resulting in putting the contact member 63 into contact with the micro switch 68. In this state, both the

micro switches

68 and 69 are closed, therefore the relay 53 is actuated to close both the

contacts

51 and 52 to hold itself energized and to excite the solenoid 54, thus opening the valve 57' to permit air to flow from the reservoir 56 to the hammer 57 while the compressor 55 continues to deliver compressed air into the reservoir 65. The air now supplied to the hammer 57 drives the piston reciprocatively in the cylinder and applies impacts to the object contacted by the tool.

When the pressure in the reservoir 56 decreases to a given value as the result of consumption of air at the piston end as described above, the valve member 65 returns to the original righthand position due to the expansion of spring 64, and the contact member 63 again contacts the micro switch 69. Both the

relay contacts

51 and 52 are opened, solenoid 54 is deenergized, and the valve 57' is closed to block the flow of compressed air from the reservoir 56 to the hammer 57. While the air flow is interrupted at the valve 57', compressed air is not consumed at the piston end of hammer 57 at all, but is accumulated in the reservoir 56, and therefore pressure is continuously increased in the reservoir 56 until it is again raised to the given value sufiicient to drive the valve member 65 of regulating valve 60 to the left.

The pressure suflicient to drive the valve member 65 leftward is the maximum pressure desired in the reservoir 56, while the pressure which permits the valve member 65 to return to the right is the minimum pressure desired in the reservoir 56. It will thus be understood that the electric control of compressed air flow produces the same effects as the foregoing pneumatic control, by the intermittent suspension method according to the invention.

The method involving retardation of the return according to the invention can be carried out in a practical manner by a pneumatic system such as is shown in FIG. 5. This pneumatic system comprises an impact hammer 76, an air compressor 74 connected by a valved pipe to an air reservoir 75 on the delivery side of compressor 75, which in turn is connected to the hammer 76 by a valved pipe, and a regulating valve 70 provided in the hammer The basic parts of the hammer 76 include a cylinder 84, a cap 81 mounted on the upper end of cylinder 84, a tool holder 87 mounted on the lower end of cylinder 84, a tool 86 slidably supported in the tool holder 87, a cap valve 82 slidably enclosed in the cap 81, and a piston 85 slidably guided in the bore of cylinder 84 and always dividing the bore 80 into an upper section 89 and a lower section 88. The cap 81 is provided with an inlet 77 for supply of compressed air from the air reservoir 75. The cylinder 84 is provided with a passage 78 within the thickness of the cylinder wall through which to supply and discharge air. The cylinder 84 is further provided with an inner port 79 connecting the passage 78 to the bore 80, and an outer port 83 conecting the bore 80 to the atmosphere.

The regulating valve 70, which is located in the inner port 79 of cylinder 84, comprises a casing 22, a valve member 20 slidably enclosed in the casing 22, and a spring 15 urging the valve member 20 to the left in FIG. 6. The casing 22 has a front axial aperture 14 opening toward the cylinder bore 80, a rear axial aperture 13 opening toward the passage 78, an upper radial aperture 19 comparatively near the rear axial aperture 13, a lower radial aperture 14' comparatively near the front axial aperture 14, and upper axial bore 17 extending from the upper radial aperture 19 and opening toward the cylinder bore 80, and a lower axial slot 49 extending from the lower radial aperture 14' and opening toward the passage 78. A threaded needle 21 extends into a junction between the upper radial aperture 19 and the upper axial slot 17, and a nut 21' is mounted on the needle to adjust the location of threaded needle 21.

In operation, this pneumatic system involving the retardation of the return, and referring to FIGS. 5 and 6, the piston 85 of hammer 76 is initially down in contact with the tool 86 which is in turn in contact with the object (not shown), with the regulating valve 70 having the valve member 20 in the lefthand position under the action of spring 15. With the parts in these positions, the air passage between the rear aperture 13 and upper slot 17 is closed at the upper radial aperture 19, while the air passage between the front aperture 14 and lower slot 49 is open through the lower radial aperture 14'. At the same time, the cylinder bore 80 has atmospheric pressure in the upper section 89 as it is in communication with the atmosphere through the outer port 83, the top of the piston 85 being at a level substantially lower than the port 83. The atmospheric pressure above the piston 85 permits the cap valve 82 to move downwardly to its normal position, thereby connecting the inlet 77 with the passage 78.

Compressed air is then delivered to the inlet 77 from the air reservoir 75 which is connected with the compressor 74. The compressed air flows from the inlet 77 to the regulating valve 70 by way of the passage 78, applying substantial pressure to the end surface of valve member and driving the valve member 20- to the right against the action of spring 15, and thereby opening the air passage between the rear aperture 13 and upper slot 17 through the upper radial aperture 19 while closing the air passage between the front aperture 14 and lower slot 49 at the lower radial aperture 14'. Thus the air is supplied to the lower section 88 of cylinder bore 80 through the rear aperture 13, upper radial aperture 19 and upper slot 17 at a flow rate which is in proportion to the size of the opening between aperture 19 and slot 17 as defined by the needle 21, and thereby increasing the pressure in the lower section 88. As a result of the pressure difference between the top and bottom surfaces, the piston 85 is lifted upward.

The ascending piston 85 closes the outer port 83. The

further rise of the piston 85 then increases the pressure above it due to the compressing of the air in the upper part of the bore 80, and therefore raises the cap valve 82 upwardly from its normal lowered position, thereby pneumatically disconnecting the inlet 77 from the lead line 78 and connecting the inlet 77 to the upper section 87 of the cylinder bore 80. With the parts in these positions, the passage 78 is open to the atmosphere, releasing the pressure from the end surface of the valve member 20 to permit the valve member 20 to return to the original lefthand position under the force of the spring 15, and therebore 80 back into the passage 78 by way of the front aperture 14, lower radial aperture 14 and lower slot 49, and is discharged into the atmosphere from passage 78. As a result of the pressure difference above and below it, the piston 85 descends, being accelerated by its own gravity and compressed air from inlet 77, until it strikes the tool 86 which is in contact with the object. The piston 85 is now back again in the original lowered position.

As long as compressed air is delivered continuously from the air reservoir 75 to the inlet 77 of hammer 76, the impact hammer 76 repeats the above-described automatic reciprocation of piston 85 in the cylinder 84 to repeatedly apply blows to the object in contact with the tool 86.

The speed at which the piston 85 is moved upwardly following each downward impact stroke is determined by the rate of air flow into the lower section 88 of cylinder bore 80 by way of the rear aperture 13, upper radial aperture 19 and upper slot 17. Given the supply capacity of compressor 74, this rate of air flow to the part of the bore under the piston 85 is in turn determined by the opening between aperture 19 and slot 17, which is defined by the position of the threaded needle 21. Therefore, the return speed of piston 85 can be set at a desired value by the needle 21 and nut 21'. The smaller the opening between the aperture 19 and slot 17 as defined by the needle 21, the slower the rate at which the air is supplied through the clearance for a given supply capacity of compressor 74. In other words, the smaller the opening between the aperture 19 and slot 17, the more the speed of the piston 85 is retarded during the return stroke followlng each impact stroke for a given supply capacity of compressor 74.

A retardation of the speed of the piston 85 during the return stroke tends to enable accumulation of compressed air in the reservoir 75, although some air is consumed to make the piston 85 ascend during the return stroke. A sufficiently retarded return stroke of piston 85 causes accumulation of sufficient compressed air in the reservoir 75 in excess of the amount necessary for causing the piston 85 to ascend during the return stroke for a given supply capacity of compressor 74. It follows that there occurs a consuming cycle and an accumulation cycle for each reciprocation of the piston 85, the former corresponding with the impact stroke and the latter with the return stroke of piston 85. During the consuming cycle, compressed air is mostly consumed at the piston end to give an impact of the required power to the object, while during the saving cycle, compressed air is mostly accumulated in the reservoir sufiicient for the required impact power of piston during the following impact stroke.

Since suflicient pressure of compressed air is accumulated in the air reservoir 75 during the retarded return stroke of piston 85, the hammer 76 continuously provides impacts of the required power to the object. The retardation of the return stroke is set at the desired value by correctly positioning the needle 21 for the supply capacity of air compressor 74 and the required impact power of hammer 76. Therefore, from a practical standpoint, with a moderate retardation of the piston return stroke, the method involving retardation of the return of the piston makes it possible for the pneumatic impact hammer to exert powerful impacts even when used with an air compressor of comparatively small supply capacity as a compressed air source.

The time-lag return method, according to the invention, can be carried out in a practical manner by a pneumatic system as shown in FIG. 7. This pneumatic system consists primarily of an impact hammer 91, an air compressor connected to an air reservoir 90' provided on the delivery side of compressor 90, which reservoir is in turn connected to the hammer. A pneumatic bypass means is provided between the reservoir 90' and the hammer 91. The hammer 91, compressor 90 and reservoir 90' of the pneumatic system are illustrated in dotted lines while the pneumatic bypass means is shown in dark lines in FIG. 7.

The hammer 91 has a cylinder which is provided with an upper port 92 and a lower port 93 in the cylinder wall for the supply and discharge of air. It is also provided with a cylinder head 40 at the top of the cylinder. A piston 99 is slidably guided in the cylinder, always dividing the bore into an upper portion 92' and a lower portion 93'.

The pneumatic bypass means illustrated in dark lines in FIG. 7 comprises an upper port valve 94, a manifold 46, a lower port valve 95, a starting valve 96, a changeover valve 97. an actuating valve 98, and a time-lag chamber 33. These seven elements of bypass assembly are pneumatically interconnected with each other by pipes.

The upper port valve 94 comprises a casing 25' provided with an axial aperture 23-3 and three radial apertures 23-1, 23-2 and 24, a valve member 25 slidably enclosed in the casing 25, and a spring 5-25 urging the valve member 25 downward. The aperture 23-2 is in communication with the upper port 92 of cylinder 91. The aperture 23-1 is located opposite the aperture 23-2, and reduced diameter portions of valve member 22 provide a passage between them when the reduced diameter portions are between these apertures. The aperture 24 is open to the atmosphere and is located just under the aperture 23-1 and also opposite the aperture 23-2 so that the reduced diameter portion of the valve member provides passage between them.

The manifold 46 is provided with an inlet 46' and six outlets 46-1, 46-2, 46-3, 46-4, 46-5, and 46-6. The inlet 46' is connected to the air reservoir 90' by way of a pipe d, while the six outlets are connected to various ports in the said 95-98 valves by way of the pipes a, b, c, e, ,f, and g.

The lower port valve 95 comprises a casing 28 provided with an axial aperture 26-3 and three radial apertures 26-1, 26-2, and 27, a valve member 28 slidably enclosed in the casing 28, and a spring 5-28 urging the valve member 28 upward. The aperture 26-2 is in communication with the lower port 93 of cylinder 91. The aperture 26-1 is located opposite to the aperture 26-2 and reduced diameter portions of the valve member 28 provide a passage between them when the reduced diameter portions are between these apertures. The aperture 27 is open to the atmosphere and is located just under the aperture 26-1 and also opposite to the aperture 26-2 so that the reduced diameter portion of valve member provides passage between them, The aperture 26-1 is connected to outlet 46-5 of the manifold 46 by pipe f.

The start valve 96 comprises a casing 44' provided with two axial apertures 43-4 and 43-5 and three radial apertures 43-1, 43-2 and 43-3, and a valve member 44 slidably enclosed in the casing 44'. A valve stem 45 extends from the valve member 44 through the aperture 43-5 and has a ball 45 on the free end thereof and a spring S-44 urges the valve member 44 inward. The aperture 43-1 is located opposite to the aperture 43-2 and a reduced diameter portion of valve member 44 provides a passage between them when the reduced diameter portion is aligned with the apertures. The aperture 43-3 is located near the aperture 43-4 and when the valve member 44 is moved to the outer position, and air passage exists between 43-3 and 43-4. The ball 45 moves into and out of the lower section 93 of cylinder bore in engageable relation with the piston 99. The port 43-1 is connected to the outlet 46-3 of the manifold 46 by the pipe 2.

The change-over valve 97 comprises a casing 37' provided with an axial aperture -14 and opposed pairs of radial apertures 35-1 and 35-7, 35-2 and 35-8, 35-3 and 35-9, and 36-1 and 35-9, 35-4 and 35-11, 36-2 and 35- 12, 35-5 and 35-13, and 36-1 and 36-4. A valve member 37 is slidably enclosed in the casing 37' and has four reduced diameter portions, one for each two pairs of opposed apertures. A valve rod 39 extends upwardly from the valve member 37 through the aperture 35-14, and a spring S-37 urges the valve member 37 upwardly. A bar 42 slidably supported in a central aperture through the cylinder head 40 depends from one end of a lever 38 rotatably supported on a fulcrum 38 and having the other end fixed to the upper end of the valve rod 39. The lower end of bar 42 is engageable with the piston 99. The casing 37' also has an aperture 36-3 on the same level as the apertures 35-2 and 35-8, and one of the reduced diameter portions of valve member 37 provides a passage to the aperture 36-3 from each of them. Aperture 35-7 is connected to outlet 46-2 of the manifold by pipe b, apertures 35-9 and 35-10 are connected to axial port 26-3 of lower port valve 96 by pipe e", apertures 35-11 and 35-2 are connected to axial port 23-3 of upper port valve 94 by pipe 0'', aperture 35-13 is connected to outlet 46-4 of the manifold 46 by pipe g, and apertures 36-1 to 36-4 are vented to the atmosphere. Aperture 35-5 is connected to aperture 43-3 of starting valve 96 by pipe g and aperture 35-6 is connected to aperture 43-4 of the starting valve 96 by pipe g".

The actuating valve 98 comprises a casing 30 provided with two axial apertures 29-6 and 29-7 and two pairs of opposed radial apertures 29-1 and 29-3 and 29-2 and 29-4, and an additional radial aperture 29-5. A valve member 30 is slidably enclosed in the casing 30', and a valve rod 32 extends downwardly from the valve member 30 through the aperture 29-7, and a spring S-30 urges the valve member 30 downwardly. Two reduced diameter portions of valve member 30 provide passages between the apertures 29-1 and 29-3 and the apertures 29-2 and 29-4 when the valve member is properly positioned, while the aperture 29-5 is located near the aperture 29-6 and when the valve member is moved out of the casing, a passage is provided between them. Aperture 29-1 is connected to outlet 46-6 of the manifold 56 by pipe 2, aperture 29-2 is connected to the outlet 46-1 of the manifold 42 by the pipe 0, aperture 29-3 is connected to the aperture 35-3 of the change-over valve 97 by pipe e, aper- 10 ture 29-4 is connected to aperture 35-4 by pipe 0', and apertures 29-5 and 29-6 are connected to apertures 35-1 and 35-8, respectively, of the changeover valve 97 by pipes b and b".

The time lag chamber 33, which has a fixed capacity, is provided with an upper aperture 31', a lower aperture 34' and a middle aperture 33. Movable through the upper aperture 31' is a head 31 in slidable and airtight relations. The head 31 is engaged with the rod 32 of the actuating valve 98. At the lower aperture 34 is provided a regulating valve 34 to regulate the air flow into the chamber 33 at a desired rate. The middle aperture 33' is for the discharge of air to decrease pressure in the chamber 33, and is connected to aperture 35-2 of changeover valve 97 by pipe (2''. Valve 34 is connected to aperture 43-2 in starting valve 96 by pipe a.

Normally, as shown in FIG. 7, the

live valves

94, 95, 96, 97 and 98 have their respective valve members kept in the normal positions by the action of the springs and their own gravities, thus opening some of the air passages while closing the others. When the respective valve members move out of the normal positions against the action of the springs, the normally opened air passages are closed while the normally closed air passages are opened.

Considering the practical operation of such a pneumatic system by the time-lag return method of the invention, and referring to FIG. 7, the piston 99 of hammer 91 is initially down in contact with the tool (not shown) of hammer 91, which is in turn in contact with the object (not shown). In this state, the piston 99 holds the ball 45 out of the cylinder bore, being engaged therewith. In other words, it holds the valve member 44 of start valve 96 outward from the normal inward position against the elasticity of spring 5-44, thereby opening the passage between the apertures 43-1 and 43-2, as well as the one between the apertures 43-3 and 43-4.

Compressed air is delivered to the manifold 46 by way of the pipe d, and at the same time to the upper section 92 of the cylinder bore by way of a pipe h, from the air reservoir 90, which is connected to the compressor 90. The compressed air is supplied from the manifold 46 to the time-lag chamber 33 through the pipe a, the now open passage between apertures 43-1 and 43-2 and pipe a, and through the regulating valve 34. The pipe (2" is closed at the aperture 35-2 in the normal raised position of change-over valve 97, so the air supplied through the regulating valve 34 increases the pressure within the chamber 33, which has a fixed capacity, in proportion to the flow rate regulated by the valve 34, and, after some time, the chamber 33 pressure reaches a given value sufiicient to raise the head 31 into engagement with the valve rod 32 against the elasticity of spring S-30 of actuating valve 98. Meanwhile, compressed air is also supplied from the manifold 46 to the start valve 96 by way of the pipe g, the open passage between apertures 35-13 and 35-5 and pipe g. The pipe g" being closed at the aperture 35-6 in the normal raised position of change-over valve 97, the air supplied by way of the pipes g and g tends to keep the valve member 44 in the outward position against the elasticity of spring S-44 even after the ball 45 is disengaged from the piston 99 after the piston ascends, so that pressure will not be released from the time-lag chamber 33 during ascending of the piston 99, as described later.

When the pressure reaches a predetermined value in the chamber 33, the head 31 begins to be raised to drive the valve member 30 upward out of the normal lowered position against the elasticity of spring 5-30. This initial rise of valve member 30 opens the air passage between the apertures 29-5 and 29-6. Then air is supplied from the manifold 46 to the actuating valve 98 by way of the pipe b, the passage between apertures 35-7 and 35-1 and pipe b. The pipe b" being closed at the aperture 35-8 in the normal raised position of change-over valve 97, the air supplied through the pipes b and b quickens the rising speed of valve member 30.

When the actuating valve 98 is in the fully raised position with the passages opened between the apertures 29-1 and 29-3 as well as between the apertures 29-2 and 29-4, air is supplied on the one hand from the manifold 46 to the upper port valve 94 by way of the pipes c, the passage between apertures 29-2 and 29-4, pipe c, the passage between apertures 35-4 and 35-11 and pipe and on the other hand, from the manifold 46 to the lower port valve 95 by way of the pipe e, the passage between apertures 35-3 and 35-9, and pipe e". The air supplied by the pipes c, c, and c" raises the upper port valve member out of the normal lowered position against the elasticity of spring S-25, thus opening the passage between the apertures 23-2 and 24, and therefore compressed air is discharged out of the upper section 92 of the cylinder bore into the atmosphere through the upper port 92 and apertures 23-2 and 24. In other words, the pressure is reduced to atmospheric in the upper section 92' of the cylinder bore. The air supplied by way of the pipe e e and e" lowers the lower port valve member 28 out of the normal raised position against the elasticity of spring S-28, thus opening the passage between the apertures 26-1 and 26-2, and therefore compressed air is supplied into the lower section 93' of the cylinder bore from the manifold 46 by way of the pipe 1 through the lower port 93. In other words, the pressure is increased in the lower section 93 of cylinder bore. As a result of the pressure difference above and below it, the piston 99 is lifted upward.

The ascending piston 99 finally engages the bar 42 near the cylinder head 40, and this rotates the lever 38 on the fulcrum 38 so as to lower the valve member 37 out of the normal raised position against the elasticity of spring 8-37. In the lowered position of change-over valve 97 with the passages open between the apertures 35-2 and 36-3, between the apertures 35-8 and 36-3, between the apertures 35-10 and 36-1, between the apertures 35-12 and 36-2, and between the apertures 35-6 and 36-4, air is no longer supplied to the starting valve 96 by way of the pipes g and g but is discharged into the atmosphere by way of the pipe g" and apertures 35-6 and 36-4, and therefore the valve member 44 returns to its original inward position by the action of spring 8-44, and the ball 45 goes back into the cylinder bore again.

Then air is no longer supplied to the time-lag chamber 33 -by way of the pipes a and a but is discharged out of chamber 33 into the atmosphere by way of the pipe a" and apertures 35-2 and 36-3 while air is no longer supplied to the actuating valve 98 by way of the pipes 17 and b but is discharged from it into the atmosphere by way of the pipe b" and apertures 35-8 and 36-3. Therefore the valve member and rod 32 are returned to the original lowered positions together with the head 31 by the action of spring S-30 plus their own gravities. Accordingly, air is no longer supplied to the upper port valve 94 by way of the pipes c, c and c", but is discharged into the atmosphere by way of the pipe c" and apertures 35-12 and 36-2. Therefore the valve member 25 returns to the original lowered position by the action of spring 8-25 plus its own gravity. Likewise, air is no longer supplied to the lower port valve 95 by way of the pipes e, e and e", but is discharged into the atmosphere by way of the pipe 2' and apertures 35-10 and 36-1, and therefore, the valve member 28 returns to the original raised position by the action of spring S-28.

In the raised position of lower port valve 95, compressed air is discharged into the atmosphere from the lower section 93' of the cylinder bore through the lower port 93 and apertures 26-2 and 27, thus reducing the pressure to atmospheric in the lower section 93'. In the raised position of upper port valve 94, compressed air is supplied to the upper section 92' of the cylinder bore from the air reservoir 90 by way of the pipe 11 through apertures 23-1 and 23-2 and the upper port 92, thus increasing the pressure in the upper section 93. As a result of the pressure difference above and below it, the piston 99 descends, being accelerated by its own gravity and the pressure above it, until it strikes the tool which is in contact with the object. The piston 99 is now back in the original lowered position again, while the change-over valve 97 has also returned to the original raised position due to the action of spring S-37 after the piston 99 is disengaged from the bar 42.

As long as compressed air is delivered continuously from the air reservoir to the pipes h and d of hammer 91, the impact hammer 91 repeats the above-described automatic reciprocation of piston in the cylinder 91' to strike blows repeatedly on the object with which the tool of the hammer 91 is in contact.

Because it takes some time to increase the pressure within the time-lag chamber 33 to a value sufficient to raise the head 31 against the action of spring S-30, there is a corresponding time-lag prior to each return stroke of piston 99, more exactly from the end of each impact stroke to the beginning of the successive return stroke. During this time lag, the piston 99 rests in the lowest position and therefore hardly any compressed air is consumed at the piston end of hammer 91, but it is accumulated in the air reservoir 99'. it follows that there occurs a consuming cycle and an accumulation cycle in each reciprocation of the piston 99. the former corresponding with the process from the beginning of each return stroke to the end of the succeeding impact stroke and the latter corresponding with the process from the end of each impact stroke to the beginning of the successive return stroke. During the consuming cycle, compressed air is consumed at the piston end to drive the piston to strike the tool and also to lift the iston 99 in the return stroke, while during the accumulation cycle hardly any compressed air is consumed at the piston end of hammer 91, but it is accumulated in the reservoir The time-lag from the end of each impact stroke to the beginning of the successive return stroke is in proportion to the flow rate at which compressed air is supplied to the time-lag chamber 33 through the regulating valve 34 for a given supply capacity of the air compressor 90. Therefore, the time-lag is given a desired value by the regulating valve 34. The longer the time-lag prior to the return stroke of piston 99, the higher the pressure accumulated in the air reservoir 90' for a given supply capacity of compressor 90. A sufficient time-lag accumulates sufficient pressure in the reservoir 90 before the return stroke of piston 99.

Since compressed air at sufiicient pressure is accumulated in the air reservoir 90 during the time-lag from the end of the impact stroke to the beginning of the return stroke, a hammer 91 always strikes the tool with the required power. The time-lag is set at a desired value by the regulating valve 34 in relation to the supply capacity of air compressor 90 and the required impact power of hammer 91. Therefore, from a practical standpoint, with a moderate time-lag prior to the piston return stroke, the time-lag method of the invention makes it possible for the pneumatic impact hammer to exert very powerful blows while using an air compressor having a comparatively small supply capacity as a compressed air source.

It will thus be seen that by any of the improved methods of controlling the pneumatic supply system in accordance with the invention, the pneumatic impact hammer exerts very powerful blows While using an air compressor of comparatively small capacity as a compressed air source.

Since certain changes and modifications may be made in the invention, some of which have been herein suggested, it is intended that the foregoing shall be construed in a descriptive, rather than in a limiting sense.

What i claim is:

l. A method of controlling the tlow of compressed air from a source of continuous supply type through an air reservoir to an automatic hammer of a kind having a piston driven pneumatically to reciprocate through an impact stroke and a return stroke alternately to strike repeated blOWs on an object during the impact stroke, comprising interrupting the fiow of compressed air supplied to the piston end of said hammer intermediate said air reservoir and said piston of said hammer when the air pressure in said reservoir is lowered to a given value by at least partially blocking the flow of air to the hammer, and resuming the flow when the pressure is raised to a given value in said reservoir, thereby suspending the reciprocations of said piston intermittently, whereby alternation of a consuming cycle and an accumulating cycle for compressed air is provided in the operation of said hammer, said accumulating cycle corresponding with the suspension of reciprocations of said piston and said consuming cycle corresponding to the resumption of reciprocations of said piston, and during said consuming cycle compressed air is used mostly at the piston end of said hammer to drive said piston reciprocatively, and during said accumulation cycle hardly any compressed air is used at the piston end of said hammer, but rather it is accumulated in said reservoir so that there is sufficient compressed air for the succeeding consuming cycle, said pressure at which the compressed air flow is resumed being substantially higher than said pressure at which said compressed air flow is interrupted.

2. A method as claimed in claim 1 in which the step of interrupting the flow of compressed air comprises completely blocking the flow of compressed air for a time sufficient to allow air pressure to build up in the reservoir to the desired level.

3. A method as claimed in claim 2 in which the step of interrupting the flow of compressed air comprises sensing the pressure of the air in the reservoir, and pneumatically operating valve means for blocking the air flow.

4. A method as claimed in claim 2 in which the step of interrupting the flow of compressed air comprises sensing the pressure of the air in the reservoir, and electrically operating valve means for blocking the air flow.

5. A method as claimed in claim 1 in which the step of interrupting the flow of compressed air comprises partially blocking the flow of air to the enclosed space beneath the piston of the hammer during the return stroke for causing the speed of the return stroke to be retarded, and thereby allow accumulation of air in the reservoir during the return stroke.

6. A method as claimed in claim 1 in which the step of interrupting the flow of compressed air comprises bypassing part of the flow of compressed air around the air hammer, slowly accumulating the bypassed air and increasing the pressure thereof, applying said pressurized accumulated air when it has reached a predetermined pressure to unblock the flow of the compressed air to the air hammer, and when the hammer has completed the return stroke, discharging the accumulated air, and when the hammer has completed the impact stroke, again accumulating the bypassed air.

References Cited UNITED STATES PATENTS 1,055,857 3/1913 Behr 1731 X 2,539,709 1/1951 Sykes 57 X 2,787,123 4/1957 Delvaux 6057 2,897,782 8/1959 Kennedy 6057 X 3,195,655 7/1965 Kardcn 173-1 3,398,533 8/1968 Wolfbaur 6057 NILE C. BYERS, 111., Primary Examiner US. Cl. X.R.