US3408897A

US3408897A - Fluid power hammer having accumulator means to drive the hammer through its working stroke independent of the system pump

Info

Publication number: US3408897A
Application number: US411978A
Authority: US
Inventors: Kenneth H Hoen; Walter J Chapman; Robert W Jones
Original assignee: Champion Inc
Current assignee: Champion Inc
Priority date: 1964-11-18
Filing date: 1964-11-18
Publication date: 1968-11-05
Anticipated expiration: 1985-11-05
Also published as: GB1135225A

Description

E THE 5, 68 K. H. HOEN ETAL FLUID POWER HAMMER HAVING ACCUMULATOR MEANS TO DRIV HAMMER THROUGH ITS WORKING STROKE INDEPENDENT OF THE SYSTEM PUMP 5 Sheets-Sheet 1 Filed Nov. 18, 1964 INVENTOR.

KENNETH H. HOEN WALTER J. CHAPMAN ROBERT W JONES BY AT ORNEY Nov. 5, I968 FLUID POWER HAMMER NAVING ACCUMULATOR MEANS TO DRIVE THE HAMMER THROUGH ITS WORKING STROKE INDEPENDENT OF THE SYSTEM PUMP Filed NOV. 18, 1964 5 Sheets-Sheet 2 INVENTOR. KENNETH H. HOEN WALTER J CHAPMAN ROBERT W JONES BY g z ATTERNEY K H.HOEN ETAL. 3, 08,8 7 I Ndv. 5, 1968 K. H. HOEN ETAL 3,408,897 FLUID POWER HAMMER HAVING ACCUMULATOR MEANS TO DRIVE THE HAMMER THROUGH ITS WORKING STROKE INDEPENDENT OF THE SYSTEM PUMP 5 Sheets-Sheet 5 Filed Nov. 18, 1964 INVENTOR.

H. HOEN KENNETH WALTER J. CHAPMAN ROBERT W. JONES ATTORNEX.

3,408,397 IVE THE INDEPENDENT Nov. 5, 1968 K. H. HOEN ETAL FLUID POWER HAMMER HAVING ACCUMULATOR MEANS TO DR HAMMER THROUGH ITS WORKING STROKE OF THE SYSTEM PUMP 5 Sheets-Sheet 4 Filed Nov. 18, 1964 INVENTOR. KENNETH H HOEN WALTER J. CHAPMAN ROBERT W JONES ATTORNEY Nov. 5, 1968 H. HOEN ETAL 3,408,897

K. FLUID POWER HAMMER HAVING AGGUMULATOR MEANS TO DRIVE THE Filed Nov. 18, 1964 HAMMER THROUGH ITS WORKING STROKE INDEPENDENT OF THE SYSTEM PUMP 5 Sheets-Sheet 5 INVENTOR.

KENNETH H. WALTER J. ROBERT W.

ATTERNEY 3,408,897 Patented Nov. 5, 1968 FLUID POWER HAMMER HAVING ACCUMU- LATOR MEANS TO DRIVE THE HAMMER THROUGH ITS WORKING STROKE INDE- PENDENT OF THE SYSTEM PUMP Kenneth H. Hoen, Littleton, Walter J. Chapman, Denver, and Robert W. Jones, Englewood, Colo., assignors to Champion, Inc., Englewood, (3010., a corporation of 'Colorado Filed Nov. 18, 1964, Ser. No. 411,978 24 Claims. (Cl. 915) ABSTRACT OF THE DISCLOSURE In a hydraulic hammer mechanism, the hammer weight is reciprocated through its working and return strokes by a ram cylinder circuit, the latter being controlled for automatic or manual operation by a hydraulic control circuit. In either the automatic or manual position, the length of stroke, speed, power and balance of the ram cylinder may be independently regulated. Moreover the ram cylinder is self-regulating with the necessary built-in safety features to avoid shock or damage to the mechanism or circuitry. Still further, the ram cylinder may be actuated through a power or gravity stroke as desired, and is characterized in that considerably more power and acceleration can be developed in the ram cylinder through each working and return stroke while isolating the cylinder circuit from the hydraulic control circuit.

This invention relates to fluid actuated power hammers, and more particularly relates to a vehicle-mounted hammer mechanism and a hydraulic control circuit therefor being adaptable for use in cutting, scoring or breaking concrete, tamping earth fills and in other related earth-working operations.

Mobile hammer units are conventionally designed to suspend an impact tool or other working implement at the lower end of a ram or other heavy mass which is guided for reciprocal movement alternately to perform a working, or down, stroke and a return, or lift, stroke. customarily, the hammer mechanism is mounted on a vehicle which can be advanced to the work site and be maneuvered into position for performing work; and a preferred manner of mounting the hammer mechanism and impact tool on a vehicle and for controlling the movement and disposition of the tool in relation to the work is set forth and described in detail in our copending application for United States Letters Patent entitled Mobile Hammer Unit and Position Control Apparatus Therefor, Ser. No. 411,979, filed Nov. 18, 1964, now US. Patent No. 3,333,646. Also, as set forth and described in copending application for patent entitled Hammer Tool Attachment and Tool, Ser. No. 345,006, filed Feb. 14, 1964, now US. Patent No. 3,318,392, and assigned to the assignee of this invention, various different tools may be attached to the lower end of the ram or hammer head to perform a number of different operations, and accordingly the ower requirements for the rar'n and tool will vary over a wide range depending upon the nature of work and type of tool carried by the ram. Usually, the ram is either of the gravity drop or power driven type and, in accordance with the present invention, the control circuit for the ram and tool enables operation either as a gravity drop or power hammer.

In the present invention, the ram is driven or powered by means of a fluid actuated motor, preferably in the form of a hydraulically operated power cylinder and piston, with the ram and tool supported for movement in response to reciprocation of the piston within the cylinder. In driving the tool through its working stroke, it is highly desirable that the fluid control circuit and power cylinder be so designed that the tool can be rapidly accelerated over a relatively short distance of travel to attain maximum velocity and force at impact; and in order to permit development of the highest possible impact forces, the external effect of the resultant shock or reaction at impact upon the hammer mechanism should be effectively absorbed by the vehicle and supporting assembly, and the internal etfect on the fluid system should be isolated as much as possible from the control circuit and fluid source. Moreover, on the return stroke it is advantageous initially to effect rapid acceleration under an additional force in order to free the tool in the event it should become lodged or struck in the working surface. It is important also that the power cylinder be self-regulating in order to rapidly decelerate in the event it reaches the end limit of its travel in either direction, since this will enable the operator safely to impart the maximum number of blows over a given period of time.

For maximum efiiciency and power in operation, pressure requirements are normally quite high and would normally necessitate a high capacity source of fluid under pressure. In accordance with the present invention, through the novel and most eflicient utilization of energy storing devices in cooperation with the power cylinder, the available power for the ram is far in excess of that available at the pressure source, but at the same time is closely controllable within safe limits both by the operator and automatically within the system according to the length of stroke and varying load requirements. Moreover, under remote control by the operator, at fluid control circuit permits selection of manual or automatic stroke control,

power, speed and length of stroke, as well as gravity drop or power down stroke of the impact tool.

Accordingly, a principal object of the present invention is to provide a power system for a mobile hammer unit in which the working or impact tool is operated rapidly and with a high degree of force through its entire stroke without requiring a correspondingly high power source.

Another object of the present invention is to provide a source of hydraulic fluid of relatively small output capacity in the operation of a control circuit for actuation of a working or impact tool, and wherein the circuit is capable of delivering additional operating power to the tool independently of the source under peak load conditions.

Another object of the present invention is to provide a hydraulically actuated hammer mechanism in which operation of an impact tool through its working and return stroke is effectively accomplished by interrelated but separate hydraulic control means, the operation of which is fully coordinated throughout each cycle.

It is a still further object to provide a hydraulically actuated hammer unit in which operation of the hammer tool through its working stroke is effectively isolated from the fluid source, and with provision being made for relieving the hydraulic pressure in response to excessive loads imposed on individual parts of the system so as to avoid damaging the hammer mechanism.

A further object of the present invention is to provide an automatic pilot control circuit which, according to the direction of fluid flow to and from the power hammer, will automatically control reversing of the hammer in either direction of travel and in such a way as to greatly minimize shock on the system between strokes.

It is an additional object to provide a balanced, relatively low pressure circuit for delivering power to, a hammer weight and tool in either given direction of movement and wherein the entire control circuit is sufliciently compact to permit its mounting on a vehicle under the remote control of the operator without disturbing or affecting the vehicle operation.

Other objects and advantages of the present invention will become more apparent from a consideration of the following detailed description and claims, taken together with the accompanying drawings, in which:

FIGURE 1 is a front elevational view of a preferred form of power hammer mechanism disposed for sliding movement along a hammer guide frame assembly.

FIGURE 2 is a sectional view, taken about lines 22 of FIGURE 1.

FIGURE 3 is a top plan view of the preferred form of power hammer mechanism.

FIGURES 4 and 4A are enlarged fragmentary views partially in section of the power cylinder assembly for the power hammer mechanism, in accordance with the present invention.

FIGURES 5 and 6 are diagrammatic views, with portions thereof enlarged and represented in cutaway form of a remote control valve circuit and ram cylinder control circuit, respectively, for the hydraulic control circuit, in accordance with the present invention.

FIGURE 7 is a fragmentary sectional View illustrating in detail a portion of the stroke control valve shown in FIGURE 5.

FIGURE 8 is a detailed view in section of a preferred form of pressure booster cylinder for the control circuit; and

FIGURE 9 is an enlarged view in section of a preferred form of power limit valve in the hydraulic control circuit.

Referring in detail to the drawings, there is illustrated in FIGURES 1 to 3 a hammer mechanism being broadly comprised of a hammer weight or ram 10 with an impact tool 11 suspended at its lower end, and the ram being mounted for reciprocal sliding movement along a hammer guide frame assembly 12. The detailed cOnStruction and arrangement of the hammer weight in relation to the guide frame assembly is set forth in copending application Ser. No. 411,979; and, as a setting for the present invention, generally the hammer weight 10 is of hollow heavy-walled construction with opposite elongated sides 14 slidable along the inner surfaces of a pair of vertically extending tubular track members 15, the latter being interconnected to form a rigid tower structure by means of a lower offset cross brace 16 and an upper cross brace member 18. Height adjustment of the tower structure including the hammer head and tool relative to the ground surface is suitably accomplished by slidably disposing the outer surfaces of the tubular track members in a pair of spaced outer vertical guideways 20 forming divergent extensions of a main support or frame 22 for the entire guide frame assembly; and to control height adjustment of the tower, a pair of lift cylinders 24 are positioned just rearwardly and to one side of each of the track members for connection between the stationary frame portion 22 and brackets 26 on the lower cross brace 16 of the tower structure. Although not shown in FIGURES 1 to 3 herein, the entire hammer guide frame assembly is mounted in swiveled relation to one end of an overhead boom assembly carried by a tractor vehicle so that the guide frame assembly will follow movement of the tractor and boom assembly, as well as being independently movable in relation to the boom assembly, to position the tool in desired relation to the work.

Considering in more detail the construction of the hammer mechanism, the ram 10 has a lower hollow extension 30 of reduced size which terminates in a closed lower end 32 having an adaptor 33 for attachment of the hammer tool 11, or other suitable tools or implements utilized in earth working operations. The closed lower end 32 also includes a pair of spaced upwardly directed bracket plates 34 adapted to receive a pin 35 having a generally spherical bearing 36 thereon to establish swiveled connection of the ram and attached tool with a ram cylinder assembly T. Essentially, the assembly T includes a power cylinder 40 depending downwardly from the top of the tower structure and terminating in a reinforcing sleeve structure 42, and a piston rod 43 pro jecting downwardly through the sleeve structure 42 to terminate in a yoke 44 formed for insertion of the balltype bearing 36 therein. In a manner to be described, the ram cylinder assembly T also has its upper end supported in swiveled relation by ball joint assembly 45 within the cross head or main brace 18 at the top of the tower structure, thereby suspending and guiding the ram 10 and attached tool 11 from the tower structure for reciprocal sliding movement along the track member 15. Thus, by selectively applying fluid under pressure to opposite ends of the power cylinder 40, in a novel manner to be described, the ram and attached tool are alternately driven through a working and return stroke to impart a series of blows to the surface being worked.

In the preferred form, fluid is supplied to the ram cylinder assembly T through a manifold block 47 mounted on the tower structure across the upper ends of the track members 15 and main brace 18. The ram control members are represented in FIGURE 6, but their structural mounting in relation to the ram cylinder assembly is not shown in FIGURES 1 to 3 since this relation, as such, forms no part of the present invention. However, for the purpose of compact design, the ram accumulator and over travel accumulator P are positioned within the hollow track members 15; and the check valves B and C, flow sensor assembly D and pressure booster N preferably are attached to the manifold block and are in direct communication with the manifold to control flow of fluid from the main system into the ram cylinder. Above the ram cylinder, a main pressure line 48 is shown leading from the manifold 47 to a cylinder head 50 in order to supply fluid to the upper end of the chamber formed within the power cylinder; and a feed tube 52 is shown alongside the power cylinder 40 to serve as a means of fluid connection between the manifold and the lower end of the cylinder.

Ram cylinder assembly Referring to FIGURES 3, 4 and 4A, the ball joint assembly 45 includes a housing 54 which is attached to the cross brace 18 by suitable bolts 55 and is provided with an inner bearing 56 which engages a generally spherical bearing 58 secured to the upper end of the power cylinder 40. The bearing 58 is locked in place between a lower thrust nut 59 and lower threaded end 60 of the cylinder head 50. The cylinder head has a central bore 61, and a pressure line 48 leads into one side of the head for communication through the bore 61 with the upper end of the cylinder. As best seen from FIGURE 3, a backup plug 62 is inserted radially through the body of the cylinder head at an angle to the pressure line 48 and has a rod '63 projecting outwardly into. engagement with the side of the cross brace 18. Here, the backup plug is positioned to compensate for side loads imposed on the ram cylinder under introduction of hydraulic fluid under pressure both through the pressure line 48 and feed tube 52 to the upper and lower ends of the cylinder 40. The housing 54 is provided also with a vertical through-bore 65 to receive the upper end of a rocker arm shaft, see FIGURE 2, for a stroke limit cylinder assembly U to be hereinafter described in more detail.

In order to conduct fluid to and from the lower end of the power cylinder 40, the feed tube 52 extends downwardly in spaced parallel relation along one side of the cylinder and communicates with a generally L-shaped bore 68, at the upper end of the sleeve 42, which converges laterally into an inlet port 69 formed in the wall of the cylinder in spaced relation above the lower end. In addition, a vertical bore 70 extends from the bore 68 downwardly through the body of the reinforcing sleeve for communication through lateral bore 71 and inlet port 72 with the bottom extremity of the cylinder. A check valve 73 is positioned to control introduction of fluid from the bore 70 through lateral bore 71 into the cylinder, and

suitably includes a downwardly facing check valve seat 74 and a ball 75 biased upwardly by means of spring 76 into normally closed relation against the seat. An error relief valve assembly 78 projects laterally through the wall of the reinforcing sleeve and across the bore 70 into communication with a vertical channel 79 formed between the inner surface of the sleeve and outer wall of the cylinder, and which channel communicates with the lateral port 71 inwardly of the check valve for a purpose to be described. The error relief valve includes a valve seat 80 and valve 81 biased against the seat by spring 82 so that at a selected or predetermined pressure level, the valve will open to permit fluid flow outwardly from the channel into the bore 70.

A piston 85 of elongated cylindrical configuration is mounted at the upper end of the piston rod 43 and is sized for disposition in close-fitting relation within the power cylinder alternately to impart a downstroke and lift stroke to the ram and impact tool. It will be noted that the piston has a series of axially spaced peripheral grooves 86 on its external surface and the spacing between grooves is progressively reduced from the lower to the upper end of the piston. In addition, the lower extremity of the piston rod has a grooved striker bushing 87, and the uppermost series of peripheral grooves 86 are each provided with a ring seal arrangement, represented at 90, in order to establish sealed relation between the piston and the cylinder wall. In this way, on each downstroke the piston will initially displace fluid ahead of it through the port 69, but toward the end limit of travel on each downstroke the striker bushing 87 and piston in passing over the entrance to the port 68 will tend to entrap the remaining fluid between the end of the bushing and lower end of the cylinder, forcing the fluid gradually to leak back past the end surface of the piston through the spaced annular grooves into the port 69 and into the bore 69 thus causing rapid deceleration at the end of its travel.

In order to minimize hydraulic shock on the system, uniform deceleration of the piston is achieved in a unique way from a maximum velocity, as the piston crosses the port 69, to a complete stop at the lower end limit of travel, this being accomplished by maintaining a constant pressure condition across the lower end surface of the piston once it passes the port 69. To maintain a constant pressure, the grooves 86 are formed at predetermined spaced intervals along the external piston surface, each groove having the effect of increasing resistance to movement of fluid to the port 69, so that as the number of grooves between the lower end of the piston and port 69 increases, the resistance to displacement of fluid into port 69 will correspondingly increase as piston speed is rapidly slowed toward the end of its stroke. Thus, the grooves are so spaced as to prevent reduction in pressure due to reduced speed of travel; and since there is a progressive reduction in velocity or speed of the piston the spacing between grooves is progressively reduced, in an upward direction from the lower end of the piston, in direct relation to the rate of reduction in speed or velocity.

In the event that the fluid pressure level increases beyond the constant predetermined level, the relief valve 78 is set to open at the predetermined level to permit flui-d to escape through the bore 70 into port 68. Accordingly, under uniformly decelerated motion as described, destructive hydraulic shock to the system is greatly minimized thereby minimizing the dwell time necessary between strokes and permitting a substantial increase in stroke speed without damaging the system.

The reinforcing sleeve 42 has a lower end 92 forming an extension of the lower end of the cylinder 40 with an upwardly facing striker bushing 93, backed by a seal assembly 94 including a compression spring 95, to establish sealed engagement with the lower end of the piston at its lower end limit of travel on the downstroke. On the lift or return stroke, fluid applied under pressure through the feed tube 52 will enter the port 72 and a shallow recessed area 72' surrounding the striker bushing 87 to cause initial displacement of the piston away from the striker bushing 93; then as the piston rod is forced upwardly past the port 69, fluid passes through the port 69 behind the piston to complete the lift stroke. Again referring to FIGURE 4, the bore 61 in cylinder head is reduced in size and the top of the piston is provided with a correspondingly reduced portion 96 with spaced annular grooves 97, the reduced end portion being dimensioned for movement into close-fitting relation through the bore 61. Thus, on the lift stroke, fluid is displaced ahead of the upper end of the piston through the pressure line 48 into the manifold 47, and should the piston reach its upper extreme end limit of travel, the reduced end portion 96 will move through the bore 61 thereby entrapping a portion of the fluid between the upper end of the piston and the upper end wall of the cylinder head adjacent to the bore 61 and forcing the fluid to leak under the increased resistance of the grooves 97 between the reduced end portion and wall of the bore 54 into the pressure line. Again the spacing between grooves is such that the piston is rapidly but uniformly decelerated to a complete stop at the end of its stroke.

Hydraulic control circuit Selective control of the operation of the ram cylinder assembly is obtained by means of a novel hydraulic control circuit shown in FIGURES 5 and 6. FIGURE 5 illustrates the system supply and remote control valves accessible to the operator, and FIGURE 6 illustrates the ram cylinder assembly T and associated cylinder controls on the manifold 47 which, in cooperation with the remote control valves, will determine the power, speed, direction and length of stroke of the ram and impact tool. Referring generally to FIGURE 5, a primary source of hydraulic fluid under pressure is represented as consisting of a main reservoir 100 leading through a constant pressure tank 101 to a pressure-compensated variable volume pump S; and a suitable system return including an oil cooler is designated at 102. For purposes of illustration, the pump S may be of relatively large capacity and capable of supplying fluid at the desired volume and pressure, for instance on the order of 2200 pounds per square inch, and likewise at the desired high rate of flow, for example, on the order of 20 gallons per minute and may be controlled for on-off operation by a three-way valve represented at X, the latter having a pump shut-off line 103 to the pump and another fluid line 104 into the control circuit for porting fluid out of the system when the pump is not in operation. The pump operates to supply fluid under pressure through main supply line 105, and from this supply line 105 a branch line 106 leads to system accumulator V, branch line 107 leads to a power limit valve W, and a branch line 108 leads to flow control valve A. Briefly, the valve A may be described as the central control valve for the entire circuit as it controls the direction of fluid flow to the cylinder in order to drive the ram piston 85 through each stroke. At one end of the control valve A is a selector valve K which, under the direct control of the operator, will set the ram either for power down or gravity down movement. Also, under the control of the operator, an automatic-manual selector valve I will, when shifted to the automatic position, cause the ram to operate continuously through the desired number of cycles; or when shifted to a manual position permit the operator to control movement of the ram throughout each stroke by means of a manual stroke control valve Y. In either the manual or automatic position, the operator may control stroke length by means of the control valve E, control downstroke power by regulating the limit valve W, and control return or lift stroke speed by regulating valve H. Referring to FIGURE 6, the ram cylinder assembly is represented at T, and the piston 85 is powered through its downstroke or working stroke by an energy storing device defined here by ram accumulator Q, which selectively applies fluid pressure, under the control of pilot check valve B, to the line 48 into the cylinder head 50. The ram accumulator Q is charged by the system accumulator V, shown in FIG- URE 5, through line 107 from the power limit valve W. Here, a pressure differential is established between the system accumulator V and the ram accumulator Q such that when the power limit valve W opens the line 107, fluid flows under pressure from the system accumulator to charge the ram accumulator for the power down stroke. To supplement the fluid under pressure supplied from the ram accumulator Q during the downstroke, fluid displaced by the piston through the lower end of the cylinder is returned, by way of the feed tube 52 through a fluid displacement circuit defined by line 114 to pressure booster N, line 115 to flow sensor D to line 116 and through pilot check valve C to line 118 into the pressure line 48 at the upper end of the cylinder. Therefore, assuming that both pilot check valve B from the ram accumulator and pilot check valve C are open, pressure is applied to the upper end of the cylinder both by the accumulator Q and by displacement of fluid from the lower end of the cylinder during the downstroke; and by blocking return flow from the lower end of the cylinder to the main reservoir, an isolated or closed circuit is formed throughout the working stroke. Moreover, the ram cylinder assembly will act much in the manner of a displacement pump under the combined force of fluid applied from the accumulator and fluid displacement circuit to force the ram and attached tool through the power down stroke. This has the important advantage of permitting the ram accumulator to be pressurized or charged to a capacity well beyond that of the main pump, and to supplement the fluid pressure from the ram accumulator with the fluid displaced from the lower end of the cylinder, both to generate a greater working force behind the piston and also to remove from the system return line and main reservoir any shock otherwise introduced by the sudden displacement of fluid from the lower end of the cylinder.

In the remote control valve assembly, essentially the power down stroke is initiated by pressurizing line K from the selector valve K to open the pilot check valve B and by pressurizing line 1 leading from the selector valve J to open the pilot check valve C for communication of the accumulator Q and fluid displacement circuit with the upper and lower ends of the ram cylinder assembly T. Simultaneously, the control valve A is shifted to a position blocking return flow through the line 112 and exhausting the inlet line 108 to the system return 102. In addition, a check valve 124 in the lift line 110 serves to block return flow through this line from the fluid displacement circuit.

The lift or return stroke of the piston 85 in the power cylinder is initiated by allowing the pilot check valves B and C to close when the main stroke control valve A is shifted to a position which will establish fluid communication between the supply line 108 and lift line 110, return line 112 exhausting fluid from the upper end of the cylinder through the system return 102. Since pilot check valves B and C are closed, fluid applied under pressure through the line 110 will flow in a reverse direction -in succession through lines 116, 115, 114 and the feed tube 52 to the lower end of the cylinder in order to im part lift pressure to the piston. Of particular note is that under reverse flow of fluid through the pressure booster N to the lower end of the cylinder, fluid is initially supplied under increased pressure by the pressure booster to eflect rapid initial acceleration of the piston whereby to overcome any initial resistance to upward movement of the tool, such as for instance, if the tool has become lodged or stuck. At the same time, fluid displaced through the upper end of the cylinder is exhausted through the return line 112 to the system return 102.

Stroke length control The stroke length of the ram is regulated through the trip cylinder assembly U. As shown in FIGURE 4, the trip cylinder assembly is arranged in closely spaced, parallel relation to the ram cylinder and includes a rocker arm shaft which is slidable in the through-bore 65 on the housing 54, and pivotally secured at its upper end to one end of a rocker arm 132 on the manifold 47; and the lower end of the shaft is attached to the top of a single acting piston cylinder unit 134. A piston rod 137 projects downwardly through the lower end of the cylinder and in a conventional manner may 'be frictionally held by suitable packing in the lower end, not shown, so that its extent of downward projection in relation to the cylinder is determined by the volume of fluid supplied through pressure-return line 138 to the upper end of the cylinder as controlled by the stroke length valve E.

The stroke length valve E is represented as a three-way closed center, center hold position valve and includes a suitable control lever 140 for actuation of a valve spool 142 against centering spring 143. Line 144, from the main supply line 108, communicates through orifice 145 with inlet port 146; and outlet port 147 communicates with the pressure-return line 138, the latter passing through an overtravel accumulator -P to the top of trip cylinder 134 as described. By shifting the valve spool to the right, as viewed in FIGURE 5, from its center closed position, communication is established between the line 144 and the pressure return line 138 to apply fluid under pressure to the trip cylinder 134 thereby forcing the trip cylinder rod 137 downwardly through the cylinder to set it at the desired position; or by shifting the valve spool to the left, the inlet port 146 is blocked and communication established from the outlet port 147 to the exhaust port 152. A relief valve including valve element 154 and spring 155 is disposed in groove 156 opposite to the inlet and outlet ports, the relief valve being set to open below the precharge pressure of the overtravel accumulator P in order to prevent excessive charging of the accumulator above a predetermined pressure level. In turn, the orifice 145 in the line 144 primarily serves to restrict fluid flow and consequent speed of movement of the cylinder rod 137 through the cylinder 134 when lowered to the desired position. The trip cylinder rod 137 is engaged by the lower end of the ram during the lift stroke to force the rocker arm shaft 130 upwardly to pivot the rocker arm 132 and briefly, through rocker arm shaft 158, to shift the pilot valve F into position in preparation for the next working or down stroke. To prevent damage to the rocker arm linkage due to overtravel of the ram piston 85, the trip cylinder rod 137 is allowed to continue upwardly through the trip cylinder, after the rocker arm shaft 130 has reached its limit of movement, by permitting fluid to escape from the trip cylinder 134 into the overtravel accumulator P. Subsequently, when the ram piston is reversed in movement for the working stroke, the piston rod 137 is released by the lower end of the ram thus permitting fluid return through the upper end of the cylinder 134 from the overtravel accumulator P, and forcing the piston rod 137 to its original extended position as initially set by the stroke length control valve E. Essentially, the trip cylinder is single acting so that the piston rod 137 is positioned in the cylinder according to the volume and pressure of fluid acting across its top surface. Thus, to lower the piston rod, the valve E is actuated to supply fluid under pressure to the trip cylinder, as described; to raise the cylinder rod, the valve E is shifted to withdraw fluid from the trip cylinder, and at the same time the ram is lifted to engage the cylinder rod and advance it upwardly to the desired setting.

Pressure booster The pressure booster N functions in a unique manner to increase fluid pressure applied to the lower end of the cylinder 40 against the ram piston at the beginning of the lift stroke. Referring to FIGURES 6 and 8, the pressure booster N consists of an elongated body 160 having a central chamber 164 with an upper port 161 connected to line 115 and a lower port 162 connected to line 114. The upper end of the body is closed by an end cover 165, and the opposite lower end has a rod displacement chamber 166 with a pressure balance port 163 for connection of line 112' into the return line 112. A piston rod assembly includes a piston rod 167 and differential piston 168 which works in sealed relation through the chamber with a reduced extremity 169 at its upper end movable into a shallow recess 170 formed in the end cover, the recess being in communication with a bypass opening 172.

Beneath the lower port 162, the body is formed for insertion of suitable packing including V-shaped annular seals 174 and a packing spring member 175 biased against the stop washer 176. A lower end cap 178 serves to hold the packing in place with the washer 176 disposed to provide a hard positive stop' for the piston. A bleed orifice 180 from the lower port 162 is angled downwardly into the central chamber above the stop washer 176 to cushion movement of the piston 168 against the stop washer 176. Accordingly, at the beginning of the downstroke, the chamber 166 is pressurized through the return line 112, and fluid displaced from the lower end of the ram cylinder through the line 114 passes initially through the orifice 180 into the lower end of the chamber 164 against the undersurface of the piston to cause upward displacement of the piston 168 and rod 167 until the piston 168 moves past the port 162. Thereafter, fluid flow through the lower port 162 will continue to force the piston upwardly past the upper port 161 into raised position for the next lift stroke, the piston "being held in the raised position throughout the rest of the downstroke. In this relation, during downstroke movement of the power ram, the pressure booster merely serves as a conduit in the fluid displacement circuit for passage of fluid from the lower end of the ram cylinder to the upper cylinder head.

Conversely, when the ram is to be actuated through the lift stroke, the direction of fluid flow is reversed through the pressure booster and enters the upper port 161 initial ly for flow into the annular space between the chamber 164 and piston rod 167 through the lower port 162. Simultaneously, fluid is exhausted from the rod displacement chamber 166 into return line 112, and fluid pressure from line 115 through the upper bypass line 172 is suflicient when combined with the pressure differential between chamber 164 and chamber 166, to advance the piston downwardly from its raised position; from the end cover and past the port 161; and thereafter, fluid under pressure introduced through the port 161 will act across the upper surface of the piston to rapidly accelerate its downward movement through the chamber 164. As a result, fluid displaced ahead of the piston through the lower port to the lower end of the ram cylinder, by way of line 114 and feed tube 52, is substantially increased in pressure or intensified to rapidly accelerate movement of the ram piston 85 at the beginning of its lift stroke. Most desirably, the length of travel of the piston 168 in the pressure booster is relatively short compared to the return stroke travel of the ram piston so that fluid pressure is boosted only during initial movement of the ram piston, again to apply the necessary force to free the impact tool in the event it should become lodged or stuck, as well as to speed up the return or lift stroke movement of the ram.

To permit continued flow of fluid from the pressure booster to the ram cylinder after the booster piston 168 has reached its lower end limit of travel, a check valve 181 is disposed across auxiliary bore 182, the latter being directed upwardly through the body of the cylinder from the lower port 162 and terminating in a lateral port 183 leading into the chamber 164 above the piston. It will be noted that the check valve is disposed across the bore 182 and has a spring-biased poppet valve 184, the end of which normally closes the lateral port 183. The poppet valve is set to open at a predetermined pressure level so that when the piston 168 completes its stroke, the valve opens to admit fluid through the bypass or auxiliary bore 182 and, by way of orifice 180, through the port 162 to the lower end of the ram cylinder.

F low sensor assembly and automatic pilot control In general, the flow sensor assembly D operates when the ram piston has reached the end of its working or return stroke to determine the direction of fluid flow through the fluid displacement circuit to and from the lower end of the cylinder 40; and in cooperation with the automatic pilot control valve F to reverse the stroke of the ram piston during automatic cycling of the ram. For this purpose, the flow sensor includes an outer casing 190 with a cover 191 at one end and upper and lower ports 192 and 193 communicating with a central chamber 194 in the casing. Disposed for axial movement through the casing is a valve spool rod 196 which forms an extension of the rocker arm shaft 158, and an outer spool in the form of a sleeve 198 is disposed in spaced outer concentric relation to the rod with an internal spring 199 disposed between a pair of axially spaced

bushings

200 and 201 on the valve rod; keepers 202 at opposite ends of the bushings serve to center the spool over the end bushings and internal spring. In addition, the spool sleeve 198 has an orifice 203 and an external peripheral shoulder or land 204; and when the spool is centered, external shoulder 204 is aligned with an internal shoulder or land 206 in the wall of the casing to form a seal between the ports 192 and 193, with the exception of a bleed orifice 207 in the wall of the casing. It will be seen that fluid flow from the line through port 192 will act downwardly on the spool sleeve 198, and under pressure will cause axial movement of the sleeve and upper bushing against the internal spring, causing the spring to compress against the lower bushing and the shoulder 204 to be forced away from the internal shoulder 206 to open the chamber for communication between the ports 192 and 193. Conversely, flow from the opposite line 116 through the port 193 will tend to force the spool sleeve 198 upwardly in the same manner to establish communication between ports but in the opposite direction. The orifices in the shoulder 206 and the spool sleeve 198 are intended merely to maintain balanced pressure conditions within the flow sensor assembly when the spool sleeve is centered.

From the flow sensor casing, the valve rod 196 continues into the automatic pilot control valve F, the valve F having a casing 210 formed as an axial extension of the flow sensor casing with coaxially aligned central chamber 212 for movement of the valve rod 196 therethrough. In turn, the lower portion of the valve rod includes axially spaced

spool portions

213, 214 and 215 in the valve F and terminates in a lower end 216 provided with a lock nut 217 abutting against a return spring 218, the latter being positioned within an end cap 220 at the lower end of the valve casing 210. The return spring 218 is mounted on a centering pin or limit stop 222 and is biased to urge the valve rod upwardly to a raised position as illustrated in FIGURE 6.

Communicating with the central chamber in the valve body 210 are a series of pilot control lines including a pressure supply line W from the power limit valve W, control lines F and F to the automatic-manual selector valve and exhaust line F discharging to the system return. When the valve rod is in its raised position under the urging of the return spring 218, the line W communicates with control line F and control line F discharges through exhaust line F When however the rod is actuated downwardly, as by tripping the rocker arm and rocker arm shaft 158, the rod is moved to a position to establish communication from pressure line 11 W to pilot control line F and F communicates with exhaust line F In shifting the valve rod 196, it will be noted that the flow sensor spool sleeve 198 will follow its movement and also be movable independently in response to fluid flow through the fluid displacement circuit. For example, in the raised position the spool sleeve is disposed to move upwardly, in response to fluid under pressure through the lower port 193, away from the shoulder 204, to permit continued fluid flow to the lower end of the ram cylinder during the lift stroke; and when the rocker arm is tripped and the valve rod lowered at the end of the lift stroke the spool sleeve will be urged in the opposite direction by the rod 196, against fluid pressure, in preparation for the next downstroke. In the latter position, the spool sleeve will open the chamber in response to fluid flow through port 192 from the lower end of the ram cylinder during the downstroke so as to hold the pilot valve rod in position throughout the downstroke. At the end of the downstroke in the absence of fluid under pressure flowing into port 192 from the lower end of the ram cylinder, the return spring 218 will return the valve rod 196 and spool sleeve 198 to the raised position for the next stroke or cycle.

Pilot check valves The pilot check valves B and C are correspondingly formed to control admission of fluid under pressure to the top of the ram cylinder from the ram accumulator Q and from the lower end of the ram cylinder through the fluid displacement circuit as described, and accordingly like parts of the valves B and C are correspondingly enumerated. Essentially, each pilot check valve includes an outer casing 230 having a lower outlet port 232 connected through line 118 to line 48 into manifold 47, and an upper inlet port 233 communicating with main valve chamber 234. Inlet port 233 for valve B connects through line 107 with the ram accumulator Q; whereas, port 233 for valve C is connected in line 116 of the fluid displacement cir cuit. A main valve portion in each of the valves B and C controls flow between the inlet and outlet ports in each valve. Each valve portion includes a hardened valve seat 235 within the chamber below the inlet port 233, and a valve element 236 of hollow generally cylindrical configuration is slidable within the valve casing having a lower closed end, except for limited opening 237, which abuts against the valve seat 235. In addition, an orifice 234 extends through the wall of the valve element 236 for comrriunication between the inlet port and interior of the valve element 236.

Normally, the valve element 236 is biased into closed relation against the valve seat 235 by return spring 238 which is provided with a pilot valve or spring seat 239 for ball valve 248 at the upper end of the axial opening 237. Initial movement of the spring 238 away from the valve element 236 is controlled by a pilot control piston 240 movable in a separate lower chamber 242 and having a piston rod 243 extending upwardly toward the check valve element 236 and terminating in a recessed end 244 in which is positioned a floating pin 245. The pin is aligned for movement in response to movement of the piston rod through the limited opening 237 in the check valve element to control movement of the valve member or ball 248 which seats between the end of the opening 237 and spring seat 239. In this manner, the check valve element 236 will minimize surging and sudden pressure increases as the valve opens, since the piston rod 243 first must force the pin 245 upwardly to disengage the pilot valve 248 to permit initial flow from the inlet port 233 through the orifice 234 and opening 237 into the outlet port 232; and under continued movement of the piston, the upper end of the piston rod will engage the valve element 236, forcing it away from the valve seat 235 to move the check valve to a full open position establishing communication between the inlet and outlet ports.

Each pilot check valve is biased to the closed position by the return spring 238 acting against the check valve element 236 and by fluid pressure line W also leading into the lower port 249 communicating with the lower pilot piston chamber 242 above the piston 240. Lower pilot control port 250 communicates with the lower end of the valve chamber 242 behind the piston, and pilot check valve B receives its initial opening pressure from line K leading from the valve K, whereas pilot check valve C receives initial opening pressure from branch line J of control line J leading from selector valve J. Briefly, in a manner to be described, if both pilot check valves B and C are open, fluid is applied under pressure to the upper end of the cylinder both from the ram accumulator Q and the lower end of the ram cylinder T for the power down stroke; but in the event that a gravity down stroke is desired, the pilot check valve C in the fluid displacement circuit is open and the pilot check valve B remains closed, so that fluid is displaced only from the lower end to the upper end of the cylinder under the weight of the ram and impact tool causing the ram piston to move downwardly through the cylinder.

Remote control valve assembly Reference is made again to FIGURE 5 for a more detailed explanation of the main hydraulic system and remote control valve assembly. Although not shown, all hand-actuated controls for operating the hammer mechanism are preferably in a centralized location accessible to a single operator; and to correlate actuation of the control valves with operation of the hammer, all stroke control signals are applied through the main stroke control valve A, whether for manual control or automatic cycling of the hammer mechanism.

More specifically, it will be seen that the valve A is positioned between the supply line 108 and the lift and return lines 110 and 112 respectively to and from the ram cylinder control circuit, and also controls actuation, through the valve K, of the power limit valve W in the accumulator circuit. Thus, for the lift stroke, the valve A is shifted to the right to established a circuit from the supply line 108 through the lift line 110 to the lower end of the ram cylinder and simultaneously will operate, through valve K, to open the power limit valve thereby to permit charging of the ram accumulator by the higher pressure system accumulator throughout the lift stroke. On the downstroke, the stroke control valve A is shifted to the left in the relation shown in FIGURE 5 and functions to block flow of fluid to and from the lift and return lines 110 and 112, respectively, as well as to permit return of the power limit valve to a closed position, thus blocking return flow from the ram cylinder and cooperating to isolate the ram cylinder circuit throughout its downstroke.

In the preferred form, valve A consists of a valve body 260 having a supply port 262 from line 108 together with lift line port 263 and return line port 264, all in communication with a central valve chamber 265. Slidable in the chamber is a valve cycle spool 266 having a reduced end portion 268 with servo piston 269 projecting from the reduced end portion through a bore 270 in the control valve K. A port 272 at the end of the bore is provided for connection line 273 from the main supply line 108. Also, a spool shift spring 274 is disposed on the reduced end portion between the spool proper and a stop element 275 at the end of the valve A.

The opposite end of the main valve spool 266 includes a servo piston 276 having an end port 277 for connection of pilot control line 1 from the automatic-manual selector valve I. Essentially, pressurizing the pilot control line J will force the servo piston to the right, overcoming the force of the shift spring 274 and the fluid acting against the piston 269, to establish communication between the supply port 262 and lift line port 263, as well as between the return line port 264 and an exhaust port 275 to the system return. When pressure is removed from the pilot control line I for example, to signal the end of the lift stroke, the shift spring 274 and piston 269' will return the valve spool to a position blocking flow between the return line port 264 and exhaust port 275. In this way, the servo piston 269 in cooperation with the shift spring 275 is effective to rapidly shift the main control spool to a position blocking the supply port 262 and return port 263 prior to initiation of the downstroke, thereby insuring that the control valve A is closed before the pilot check valves B and C are opened at the start of the downstroke.

In order to control the speed of opening movement of the valve spool 266 for the lift stroke an orifice check valve 280, shown in FIGURE 7, is positioned in the valve body 260 opposite the reduced end portion 268. The orifice check valve is provided with a valve body 282 disposed across an exhaust port 283, the body having an orifice 284 between the exhaust port 275 and the chamber area 285 surrounding the reduced end when fluid pressure is applied through line J against the servo piston 276 to initiate the lift stroke, the check valve closes and fluid trapped in chamber 285 must bleed through the orifice 284 in order to permit the spool 266 to shift. Thus, the check valve will resist spool movement to a certain extent and prevent sudden movement or slamming of the valve spool 266 in opening the supply port 262 at the beginning of the lift stroke.

As previously stated, the ram may be actuated through its power down stroke by opening both valves B and C, or may merely be actuated through a gravity down stroke by opening only the check valve C in the displacement circuit. This selection is made by actuation of the selector valve K which has a valve spool 290 movable through chamber 292 on the side of the stop element 275 opposite the main spool for control valve A. Communicating with the chamber 292 is pilot control line J from the selector valve I and control line K leading to pilot check valve B. In addition, a pilot control line K leads from a port 94, shown dotted, in the valve K to pilot limit valve W; and the line K is selectively pressured through bore 295 extending from the lift line port 263 into the pilot control chamber 292 adjacent to the port 294. The spool 290 is shifted, to selectively open and close the lines I and K and K by means of a manual push-pull knob 296; and by inward displacement of the spool to power down position the control surfaces on the spool are aligned to establish a circuit from line I to line K for opening pilot check valve B to permit fluid flow from the ram accumulator Q to the ram cylinder. Moreover When the main spool 266 is shifted for the lift stroke, the lift line 110 being open will deliver fluid through the bore 295 and port 263 to pressurize control line K leading to power limit valve W to open same and permit charging of the ram accumulator for the next power down stroke.

In order to set the valve K for a gravity down stroke, the selector valve spool 290 is displaced outwardly by the control knob 296 to interrupt fluid flow between the control lines I and K while permitting the line K to discharge through bore 295 past the spool 266 to exhaust port 275. In this way, the pilot check valve B remains closed during the down stroke, as does the power limit valve W to prevent charging of the ram accumulator during the lift stroke; and only the pilot check valve C is opened by control line J to form a circuit for flow from the lower to the upper end of the ram cylinder and allow the ram piston 85 to fall under the weight of the ram 10 and tool 11.

Now considering in more detail the construction and arrangement of the power limit valve W as shown in FIGURE 5 and in more detail in FIGURE 9, it is responsive to pressurizing of the control line K from the selector valve K to open the line 107 between the system accumulator V and ram accumulator Q, and will permit charging to a predetermined level by means of a mallual control setting on the valve. Referring to FIGURE 9, the valve has a valve body 300 with a main valve chamber 301 for a valve spool 302 positioned therein. Communicating with the valve chamber is a post 304 for pressure line W leading to the pilot valve F, and an inlet port 305 and outlet port 306 provide pressure connections for line 107 extending from the system accumulator V to the ram accumulator Q. Preferably, the inlet port 305 is in the form of a broad open port extending upwardly through the thickness of the valve body and the central chamber 301 into the bore 304. Accordingly, the inlet port 305 is in constant communication with the pressure port 304 for line W whereas communication between inlet port 305 and outlet port 306 is of course controlled by movement of the spool 302 in the valve chamber. Initial setting of the spool 302 in relation to the ports is controlled by a screw adjustment member 307 including a threaded stem 308 disposed in a threaded end portion 309 for projection into the chamber 301 from one end of the valve, and the stem is provided with a return spring 316 extending through a bore 318 in one end of the spool. A piston chamber 310 is disposed at the opposite end of the valve body and in which is positioned a servo piston 312 with port 313 communicating with the piston chamber from the control line K At the beginning of the lift stroke, when the control line K from the valve K is pressurized to apply fluid under pressure to the port 313, the servo piston 312 is displaced to shift the spool through the valve chamber 301 against the end of the stern 308 to open the outlet port a predetermined extent, depending upon the setting of the stem 308 in the chamber. When fluid is exhausted through the pilot control line K the return spring 316 will return the spool 302 to its initial setting thus blocking flow between the inlet and outlet ports; this action will occur at the end of the lift stroke.

It will be seen therefore that the ram accumulator Q is charged a predetermined amount dependent upon the screw adjustment setting of the power limit valve W together with the length of stroke setting by valve E, since the latter will determine duration of charging and the volume of fluid that will pass from the system accumulator V to the ram accumulator Q during the lift stroke. Again, the pilot control line K is exhausted at the end of the lift stroke when the stroke control valve A returns to its position blocking the port 262 while relieving pressure from the line K to the exhaust port 275.

In order to control lift stroke speed and balance, a. conventional throttle valve H is disposed in the supply line 108 to the main control valve A and merely functions to throttle flow by means of a manual adjustment knob 320. Again, in somewhat the same manner as the power limit valve W, by adjusting the knob 320 in desired relation within the valve body, a spool, not shown, is positioned to control capacity of flow from an inlet port 323 through outlet port 324. Therefore, the valve H may be closely controlled by the operator to regulate the rate of fluid flow from the pumps to the lower end of the ram cylinder, and consequently regulate speed of travel in cooperation with the pressure booster N of the ram piston through its lift or return stroke.

From the foregoing description, it will be noted that by transmitting the appropriate fluid control signals to the valve A and to the pilot check valves B and C the hammer mechanism can be operated in either direction or continuously operated through one or more complete cycles. In accordance with the present invention, the entire circuit is set either for manual or automatic operation by manual-automatic selector valve I In FIGURE 5, the valve I is represented as a two position double selector valve including a valve spool 330 and a manual control knob 332 to shift the spool 330 either to a manual position establishing communication from manual control lines M and M to outlet lines J and J respectively; or to an automatic position forming a similar circuit from automatic control lines F and F to the lines I, and I respectively. In other words, line I, may be pressurized either by control line F or M and line J may be pressurized either by control line F or M depending upon whether the valve J is set at its automatic or manual position.

The control lines M and M lead from a manual stroke control valve Y, suitably being of the type referred to as a three position, four-way, closed center, cylinder float position valve. In construction, the valve is shown having a manual control lever 334 to shift valve spool 335 in either direction from its center hold position to control the introduction of fluid under pressure from line 336 to line M or M In the center hold position, lines M and M are discharged through exhaust ports 338 to the system return, and the supply line 336 from the main supply line 108 is blocked. Assuming that the selector valve J is in the manual position as described, then by shifting the manual valve spool 335 to the right, or to the down position, a circuit is established from supply line 336 to control line M and, through valve I, to control line J leading to line J and valve K; and at the same time line M discharges fluid from line I through an exhaust port 338. By shifting the manual spool 335 to the left, or to its lift position, a circuit is established from supply line 336 to control line M and, through valve J, to servo control line J for the valve A, while at the same time exhausting control line M for fluid return from the line J through the exhaust port 338. When the manual control lever 334 is released, a centering spring 339 at one end of the spool 335 automatically returns the spool to the center hold position exhausting both control lines M and M while permitting the pilot check valves B and C to close thereby holding the ram piston in position.

When the selector valve J is shifted to the automatic position, alternate pressurizing of control lines F and F automatically in response to movement of the flow sensor assembly D and the pilot valve takes the place of selective shifting of the valve to pressurize lines M and M as described. Accordingly, it will be seen that at the beginning of the lift stroke the flow sensor assembly D is in its raised position so that fluid flowing through lift line 110 from the control valve A passes through the lower port against the flow sensor spool sleeve 198 to urge it upwardly away from the internal shoulder 206 for flow through the pressure booster to the lower end of the ram cylinder in order to raise the ram piston through the ram cylinder.

As the ram approaches its upper limit travel, depending upon the setting of the trip cylinder U, the lower end of the ram will engage the trip cylinder rod causing it to move upwardly and pivot the rocker arm shaft 158 and attached valve rod 196 downwardly. Downward movement of the rod will overcome fluid pressure acting against the spool sleeve 198 and, in cooperation with the internal spring 199, force the spool sleeve 198 downwardly to return to closed relation against the internal shoulder, thereby interrupting fluid flow to the lower end of the ram cylinder. Simultaneously the lower spool assembly on the valve rod 196 is shifted to a position establishing communication between pressure line W and pilot control line F thereby pressurizing the control line J through the selector valve J to open one or both pilot check valves B and C, while exhausting line J through line F to the exhaust port line F Of course, both valve lines K and 1;, are pressurized in response to pressurizing pilot control line F assuming that the valve K is in the power down position, to initiate the down stroke. Through the downstroke, the flow sensor assembly valve rod 196 is held down, since fluid displaced from the lower end of the ram cylinder into the flow sensor assembly D will act against the upper end of the spool sleeve 198 in passing through the assembly D to the upper end of the ram cylinder.

Completion of the downstroke is signaled by a loss in pressure when the ram and attached tool strike the work surface and stop moving, or when the ram piston passes the inlet port 69 and moves against the lower end of the ram cylinder under uniformly decelerated motion. Under a loss in fluid pressure the spool sleeve 198 will immediately return upwardly into sealed relation with the internal shoulder, thereby selectively blocking the fluid circuit in a direction from the lower to the upper end of the ram cylinder; and the return spring 218 will cause the valve rod and spool in the pilot control valve F to shift to a position establishing circuit flow from the line W to line F while discharging line F through port F as a result of which the main control valve A is shifted to the lift stroke position for fluid flow through lift line 110 to repeat the cycle. It is important to note in this connection that the spool sleeve 198 in the flow sensor assembly D will operate independently of the automatic pilot control valve F to sense both direction and pres sure of fluid flow through the displacement circuit once it is positioned by mechanical actuation of the valve rod 196, either in response to the return spring 199 at the end of the downstroke or in response to pivoting of the rocker arm 132 upon completion of the lift stroke.

The preferred form of hammer mechanism, under selective control of the ram cylinder circuit and remote con trol valve circuitry devised, offers a number of distinct advantages in use, and especially as adapted for use in portable or mobile hammer units.

Summarizing many of the features inherent in the operation of the hammer mechanism, when the selector valve I is shifted to the manual position, the valve A can be actuated by manual control valve Y with the valve K disposed either in the power down or gravity drop position as described. Shifting the valve Y in one direction will cause the piston to move downward, or shifting the valve in the opposite direction will cause the piston to move upward the desired distance. When the valve control lever 334 is released, the valve spool 335 returns to the center hold position causing the ram piston to stop and hold in position. For the automatic stroke cycle, the selector valve I is placed in the automatic position so that fluid flow from pilot control valve F alternately through pilot control lines F and F actuates the stroke control valve A, again to force the ram piston up and down until stopped by returning the selector valve J to the manual position. Normally, the piston 85 is reversed from its downward stroke when the impact tool strikes an object and is stopped, or is reversed, in the event of overtravel past the port 69, when it reaches the lower end limit of travel within the power cylinder. In each case the resultant loss in pressure through the fluid displacement circuit to the flow sensor D will permit the valve rod 196 to be raised by the return spring to transmit a fluid control signal through line F to the stroke control valve A to initiate the lift or return stroke. Again, fluid pressure from the valve A through lift line in the reverse direction through the fluid displacement circuit to the bottom of the power cylinder will force the ram piston upwardly until the lower end of the hammer weight contacts or engages the trip cylinder rod 137. The rod 137 will actuate the valve rod 196 downwardly through the flow sensor assembly D thereby blocking continued fluid flow to the lower end of the power cylinder and also reversing the pilot control valve F to transmit a fluid control signal through line F to the control valve A and selector valve K. Assuming that the selector valve K is in the power down position, fluid control signals are then transmitted to apply opening pressure to both pilot check valves B and C for fluid flow through the cylinder head to the upper end of the power cylinder both from the accumulator Q and by returning fluid displaced from the bottom of the cylinder through the fluid displacement circuit to the top of the cylinder. The cycle is repeated when the piston has reached the end of its downstroke or is stopped by an external force, and of course the cycle will repeat itself for as long as the selector valve J remains in the automatic position; likewise if the selector valve K were in the gravity drop position as this would effect only the opening and closing of the pilot check valve B for the accumulator Q. Moreover, the lift stroke pressure booster N will effect an initial pressure increase at the beginning of the lift stroke whether in the manual or automatic position, or in the power down or gravity drop position.

Length of stroke, speed, power and balance may be independently regulated both during automatic and manual operation, and are under the direct control of the operator at all times; yet the ram cylinder circuit is self-regulating with the necessary built-in safety features to prevent damage to the hammer mechanism, for instance, in the event that the hammer tool 11 is suddenly stopped short of its full stroke or if for any reason it should overtravel in either direction beyond its intended stroke. It is further possible to develop considerably more power in the ram cylinder circuit due to the manner in which the ram piston is displaced through the down stroke while isolating the main system from the ram cylinder circuit. As an illustration, utilizing a pump capable of developing 2200 pounds per square inch pressure with 20 gallons per minute flow, it has been possible to generate an impact force on the order of 1600 foot pounds and capable of delivering 40 to 45 blows per minute. Of course the increased power and velocity of stroke permits use of a relatively lightweight ram or hammer weight as described in our hereinbefore referred to copending application. The entire mechanism is thus highly economical, fully protected with regard to safety of both the operator and machine and completely flexible so as to enable its eflicient use in a variety of operations, such as for example, concrete breaking, scoring and cutting, tamping or earth compaction Work as well as for asphalt cutting and paving operations. For instance, in asphalt cutting operations where the tool would have a tendency to get stuck, the automatic pressure boost at the beginning of the lift stroke will supply ample force to rapidly free the tool; and, again, rapid acceleration throughout the downstroke will generate a greater force over a relatively short distance of stroke.

It is therefore to be understood that while the form of apparatus and control circuitry herein described constitutes a preferred embodiment of the present invention, various modifications and changes may be resorted to without departing from the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

1. In a fluid actuated hammer unit having a hammer weight mounted for reciprocal movement, a double acting fluid motor drivingly connected to reciprocate the hammer weight with a predetermined stroke, a motor control circuit including fluid pressure supply means being connected to apply fluid under pressure to one side of the motor to actuate the hammer weight in a given direction, a primary source of fluid pressure including a reverse flo'w circuit having means to selectively apply fluid to the opposite side of said motor for reversing the movement of said hammer weight in a direction opposite the given direction, said primary source of fluid under pressure further including a charging circuit having means for charging said fluid pressure supply means during reverse movement of said hammer Weight indepently of said reverse flow circuit.

2. In a fluid actuated hammer according to claim 1, said motor control circuit further comprising fluid pressure boosting means to initially accelerate movement of said hammer weight in the reverse direction.

3. In a fluid actuated hammer according to claim 1, said motor control circuit being further characterized by having adjustable trip means being actuated in response to distance of travel of the hammer weight in the reverse direction, and pilot control means responsive to actuation of said trip means to interrupt the flow of fluid under pressure to the opposite side of said motor.

4. In a fluid actuated hammer unit having a hammer weight mounted for reciprocal movement, a double acting power cylinder drivingly connected to reciprocate the hammer weight with a predetermined stroke, a motor control circuit including first energy storing means being connected to apply fluid under pressure to one side of said power cylinder to actuate the hammer weight in a given direction, a fluid displacement circuit for delivering fluid displaced from the opposite side of said cylinder to the one side of said cylinder to supplement the flow of fluid from said first energy storing means in driving said hammer weight in the given direction, a primary source of fluid pressure to selectively apply fluid under pressure to the opposite side of said cylinder whereby to reverse the movement of said hammer weight in a direction opposite the given direction, said primary source of fluid pressure including second energy storing means for charging said first energy storing means during reverse movement of said hammer weight, and control valve means for interrupting flow of fluid under pressure from said first energy storing means to the one side of said cylinder during reverse movement of said hammer weight.

5. In a hydraulically actuated hammer, a double acting cylinder including a ram disposed for reciprocal movement therein, an impact tool mounted for reciprocation in response to actuation of said ram, a hammer control circuit to alternately supply hydraulic fluid under pressure to opposite ends of said cylinder whereby to actuate said ram to eflect alternate working and return strokes of said impact tool, said control circuit including a source of hydraulic fluid under pressure, a ram accumulator in said control circuit for applying hydraulic fluid under pressure to one end of said cylinder to drive said impact tool through the working stroke, a system accumulator being connected to said fluid source and being operative to charge said ram accumulator during each return stroke for each next working stroke in succession, valve means in said hammer control circuit for blocking return flow of fluid to the fluid source from said cylinder when said impact tool is driven through the working stroke and control valve means for interrupting flow of fluid under pressure from said ram accumulator to the one side of said cylinder during reverse movement of said impact tool.

6. In a hydraulically actuated hammer according to claim 5, said valve means including stroke control valve means movable between a first position blocking flow of fluid from said cylinder to said fluid source and a second position for supplying fluid under pressure to the opposite end of said cylinder whereby to effect each return stroke of said impact tool, a fluid return line for fluid displaced from the one end of said cylinder during the return stroke, and a system accumulator including a flow control valve being operative in response to actuation of said stroke control valve means to the second position to charge said ram accumulator for the next working stroke during return stroke movement of said impact tool.

7. In a hydraulically actuated hammer according to claim 5, said hammer control circuit additionally including first and second normally closed pilot check valve means associated with said flow conducting means and said accumulator respectively to block flow of fluid under pressure to the one end of said cylinder during the return stroke, and reversing valve means being movable in response to the advancement of said ram to the end of each return stroke to transmit a fluid control signal for opening said first and second pilot check valve means to admit fluid under pressure to the one end of said cylinder simultaneously from said accumulator and from the op posite end of said cylinder for the next working stroke.

8. In a fluid actuated hammer according to claim 7, said hammer control circuit further including selector valve means being selectively movable to a position interrupting the fluid control signal from said reversing valve means to said second pilot check valve means whereby to selectively block fluid flow from said accumulator to the one end of said cylinder during the working stroke.

9. In a hydraulically actuated hammer according to claim 5, said hammer control circuit further including reversing valve means being movable at the end of each working and return stroke to transmit a fluid control signal for reversing the direction of fluid flow through said control circuit alternately to opposite ends of said motor, and holding means responsive to reversal in direction of fluid flow through said hammer control circuit for holding said reversing valve means in a position maintaining a continuous fluid control signal throughout each next stroke in succession.

10. In a hydraulically actuated hammer according to claim 9, said hammer control circuit being further characterized by having a rocker arm assembly associated with said reversing valve, and a trip cylinder including an adjustable trip cylinder rod being disposed to be engaged in response to a predetermined distance of travel of said impact tool in the return direction to impart limited movement of said trip cylinder and to said rocker arm assembly whereby to actuate said reversing valve at the end of the return stroke, stroke length control means to selectively apply fluid under pressure to said trip cylinder in order to position said trip cylinder rod in predetermined relation to said impact tool, and an overtravel fluid pressure accumulator to receive fluid displaced from said trip cylinder when said trip cylinder rod is displaced through said trip cylinder under continued movement of said impact tool beyond the predetermined distance of travel, said overtravel accumulator being operative to return the fluid displaced by said trip cylinder rod to said trip cylinder upon reversal in stroke of said impact tool away from engagement with said trip cylinder rod.

11. A hydraulically actuated hammer unit comprising a vertical guide frame assembly, a hammer weight including an impact tool suspended at its lower end with said hammer weight being mounted for slidable reciprocal movement along said guide frame assembly, a double acting power cylinder including a differential piston and piston rod for reciprocating said hammer weight and impact tool alternately through predetermined working and return strokes and a hammer control circuit comprising fluid supply means to supply fluid under pressure to the upper end of said cylinder whereby to actuate said piston rod through the working stroke, fluid conducting means in fluid communication with the upper end of said cylinder to deliver fluid displaced from the lower end thereof whereby to accelerate movement of said piston and piston rod through the working stroke, return stroke conducting means to supply fluid under pressure to the lower end of said cylinder whereby to actuate said piston through the return stroke, check valve means in said hammer control circuit to interrupt fluid flow from said fluid supply means and said fluid conducting means respectively to the upper end of said cylinder when fluid is applied to the lower end of said cylinder during the return stroke, said fluid supply means further including energy storing means in communication with the upper end of said cylinder, a primary source of hydraulic fluid under pressure, and relatively high pressure energy storing means connectable to said primary source and including flow control valve means for establishing fluid communication from said primary source and said relatively high pressure energy storing means to said energy storing means for charging said energy storing means during each return stroke in preparation for each next working stroke in succession.

12. A hydraulically actuated hammer unit according to claim 11, said return stroke conducting means being further characterized by including fluid pressure intensifying means being operative at the beginning of the return stroke to accelerate movement of said piston.

13. A hydraulically actuated hammer unit according to claim 11, said double acting cylinder assembly comprising a cylinder body providing an elongated cylindrical chamber, a first port at one end of the chamber, a pair of inner and outer ports arranged in axially spaced relation to one another at the opposite end of said chamber, said cylindrical piston being reciprocal within the chamber to impart a working and return stroke to said impact too], said fluid supply means being operative to supply fluid under pressure to opposite ends of said chamber to actuate said piston through a working stroke whereupon fluid between said piston and the opposite end of said chamber is normally displaced through said inner port with a series of axially spaced grooves being arranged between said piston and the chamber wall between said inner and outer ports being effective upon said piston moving through its working stroke past said inner port to impart uniformly decelerated motion to said piston by restricting the passage of fluid past said piston into said inner port, and check valve means being disposed in said outer port to selectively admit fluid under pressure into the opposite end of the chamber to displace said piston away from the opposite end for movement through its return stroke.

14. A hydraulically actuated hammer unit according to claim 13, in which axially spaced grooves are arranged on the external surface of said piston, and the spacing between grooves being progressively reduced toward said inner port to impose an increasing resistance to discharge of fluid into said inner port in direct relation to decelerated movement of said piston past said inner port.

15. A hydraulically actuated hammer unit according to claim 11, said hammer control circuit being further characterized by including stroke control valve means movable between a first position blocking flow of fluid but between said cylinder and said primary source during the working stroke and a second position applying fluid under pressure through said return stroke conducting means to the lower end of said cylinder whereby to effect the return stroke, reversing valve means being movable at the end of each working and return stroke to transmit a fluid control signal to said stroke control valve means for shifting said control valve means to the position corresponding to the next stroke in succession, and holding means being responsive to reversal in direction of fluid flow through said flow conducting means for holding said reversing valve means in a position to transmit a continuous fluid control signal whereby to maintain said stroke control valve means in the position to which it was shifted by said reversing valve means in preparation for the next stroke.

16. A hydraulic fluid control circuit comprising, in combination with a double-acting power cylinder for effecting reciprocal sliding movement of a mass alternately through a working and return stroke, a primary source of hydraulic fluid under pressure including a fluid supply circuit to supply fluid under pressure to one end of said cylinder to actuate the mass through the working stroke, a fluid displaced circuit for applying fluid displacement from the opposite end of said cylinder to the one end of said cylinder during the working stroke, a fluid return circuit to supply fluid under pressure in a reverse direction through the fluid displacement circuit to the opposite end of said cylinder whereby to actuate the mass through its return stroke, stroke control valve means being movable between a first position for blocking fluid flow from said primary fluid source to said cylinder through said fluid return circuit during the working stroke and a second position for applying fluid under pressure through said fluid return circuit to the opposite end of said cylinder, automatic pilot control means being operative at the end of the return stroke to transmit a fluid control signal to said stroke control valve means shifting same to the first position and being further operative at the end of the working stroke to transmit a fluid control signal to said stroke control means for shifting same to the second position, manual stroke control valve means being movable to transmit a working stroke fluid control signal for shifting said stroke control valve means to the first position and being further movable to transmit a return stroke fluid control signal for shifting said stroke control valve means to the second position, and an autoamtic-manual selector valve being movable to connect said stroke control valve means alternately to said automatic pilot control valve means and to said manual stroke control valve means so as to be responsive either to automatic or manual fluid control signals to actuate the mass through its working and return strokes.

17. A hydraulic fluid control circuit according to claim 16, being further characterized by fluid pressure responsive means in said fluid displacement circuit for holding said automatic pilot control means in a position in which a continuous fluid control signal is applied to said stroke control valve means holding it in the position established by said automatic pilot control means at the end of each stroke throughout each next stroke in succession.

18. A hydraulic fluid control circuit according to claim 16 further comprising first and second normally closed pilot check valve means in said fluid supply circuit and in said fluid displacement circuit, respectively, being opened in response to transmission of a fluid control signal shifting said stroke control valve means to the first position for applying fluid under pressure through said fluid supply circuit and said fluid displacement circuit to the one end of said cylinder whereby to actuate the mass through its working stroke.

19. A hydraulic fluid control circuit according to claim 18 in which said stroke control valve means includes selector valve means being movable to effect individual or simultaneous opening of said first and second pilot check valve means in response to the fluid control signal applied to said stroke control valve means at the end of the return stroke.

20. A hydraulic fluid control circuit according to claim 19 in which said fluid supply circuit includes a relatively low pressure accumulator with said first pilot check valve means being disposed between said low pressure accumulator and the one end of said cylinder, and a relatively high pressure accumulator including flow control valve means being operative in response to shifting of said stroke control valve means to the second position to charge said relatively low pressure accumulator during return stroke movement of the mass in preparation for the next working stroke.

21. A hydraulic hammer control circuit comprising, in combination with a double-acting power cylinder for effecting vertical reciprocal sliding movement of a hammer weight alternately through a working and return stroke, a source of hydraulic fluid under pressure including a fluid supply circuit to supply fluid under pressure to the upper end of said cylinder to actuate the hammer weight through the working stroke; a fluid displacement circuit for delivering fluid displaced from the lower end of said cylinder to the upper end of said cylinder during the working stroke; a fluid return circuit to supply fluid under pressure through said fluid displacement circuit whereby to actuate said hammer weight through its return stroke; stroke control valve means being movable between a first position for blocking fluid flow from said primary source through said fluid return circuit during the working stroke and a second position for applying fluid under pressure from said primary source through said fluid return circuit to the lower end of said cylinder; and an automatic reversing valve including a flow sensing chamber in fluid communication with said fluid displacement circuit, a pilot control chamber and a valve rod being mounted for axial extension through said chambers having first valve spool means in said pilot control chamber and second valve spool means in said flow sensing chamber, a fluid inlet port and a pair of outlet ports being connectable to control shifting of said stroke control valve means between the first and second positions, valve rod actuating means being operative at the end of each working and return stroke to transmit a fluid control signal from said inlet port through one of said outlet ports to said stroke control valve means for shifting same in preparation for each next stroke in succession, and said second valve spool means being responsive to directional fluid flow under pressure through said flow sensing chamber to hold said first spool means in position to transmit a continuous fluid control signal to said stroke control valve means for holding same in position through each stroke in succession.

22. A hydraulic hammer control circuit according to claim 21, in which said fluid displacement circuit includes a fluid pressure booster cylinder therein comprising a body providing a chamber, first and second ports communicating with the chamber and being connectable respectively to the flow sensing chamber in said reversing valve and the lower end of said cylinder, a piston rod assembly including a differential piston movable through the chamber in response to fluid flow from said fluid return circuit and flow sensing chamber through said first port to increase the pressure level of fluid displaced ahead of said piston through said second port to the lower end of said cylinder, and said piston being further movable in the opposite direction through said chamber in response to reverse fluid flow from the lower end of said cylinder to a position establishing communication between said first and second ports whereby to permit passage of fluid through the chamber and said flow sensing chamber to the upper end of said cylinder.

23. A hydraulic control circuit according to claim 22 being further characterized in that the distance of travel of said differential piston through said pressure booster chamber is short in relation to the length of return stroke of said hammer Weight whereby to intensify fluid pressure to the lower end of said power cylinder at the beginning of the return stroke, and an auxiliary bypass line in the body of said pressure booster cylinder to provide for continued fluid flow from said chamber to the lower end of said power cylinder when said piston is in a position blocking fluid flow through said second port to the lower end of said power cylinder.

24. A hydraulic control circuit according to claim 21, said fluid supply means being defined by first energy storing means in communication with the upper end of said cylinder, and relatively high pressure energy storing means connectable to said primary source and including flow control valve means for establishing fluid communication from said primary source and said relatively high pressure energy storing means to said first energy storing means for charging said first energy storing means during each return stroke in preparation for each next working stroke in succession, and check valve means between said first energy storing means and the upper end of said cylinder fluid being movable to open in response to the fluid control signal shifting said stroke control means to the first position to apply fluid under pressure from said first energy storing means to the upper end of said cylinder for actuating said piston through its working stroke.

References Cited UNITED STATES PATENTS 2,303,666 12/1942 Souter 91-5 2,392,471 1/1946 Fox 60-51 2,443,642 6/1942 Rockwell 91-436 2,831,461 4/1958 Kupka 91-399 2,972,863 2/1961 Hyde 60-51 3,150,488 9/1964 Haley 60-51 3,183,668 5/1965 Johnson et al. 60-51 3,237,406 3/1966 Spannhake et a1. 60-51 3,266,581 8/1966 Cooley et al 173-138 2,376,519 5/1945 Stacy 91-415 2,881,739 4/1959 Huppert 60-51 3,045,768 7/1962 Huffman 175-296 3,232,176 2/1966 Hcnning et al 91-321 MARTIN P. SCHWADRON, Primary Examiner. B. L. ADAMS, Assistant Examiner.