Fluid driven hammers

Abstract

The invention comprises a reciprocable hammer head element continuously urged by a resilient element in one direction and permamently connected with a fluid pressure expansible member in relation to be propelled in the other direction by expansion of said expansible member, and means for directing pressure fluid to said expansible member and adapted to suddenly exhaust pressure fluid from the same to free said hammer head element to be propelled by said resilient element to deliver a blow to a work-piece supported in the path of movement of the hammer head element.

Description

Fluid driven hammers are known in which a reciprocating slug or hammer member moves in a hollow frame in response to fluid pressure, usually air, in which the hammer head either is itself or is connected with a piston, the piston working in a cylinder usually forming part of the frame, the hammer member being impelled into contact with a tool slidable in the frame. Such devices are costly in that careful machining is required to produce the necessary close fits.

The present invention requires the hollow frame and the reciprocating hammer member, but the close fits are unnecessary, the hammer being urged in the direction of the tool by a resilient element or spring, but being retracted by a fluid motor, in the illustrative embodiment an elongated flexible inflatable element, known in the trade as an "air spring"; and means is provided for suddenly - virtually instantly - exhausting the air spring so that the resilient element is free to propel the hammer head into contact with the tool with little or negligible resistance from the air spring. The hammer is never disconnected from the fluid motor, so no latch or other mechanism is required to provide for such release.

The invention is in part directed to constructions adapted to quickly exhaust the pressure fluid and in part to constructions for isolating from the actuating mechanism the severe vibrations originating in the hammer head to thereby shield the mechanism from damage which otherwise might be caused by such vibration. Accordingly it is an object of the invention to provide a fluid actuated hammer which will be simple, inexpensive, durable and when necessary, easily repaired.

Further objects and advantages will appear from the following specification and accompanying drawings, in which

FIG. 1 is an axial sectional view of a hammer structure embodying the invention:

FIG. 2 is an enlarged detail of construction indicated in FIG. 1:

FIG. 3 is a similar view with the parts in a different position;

FIG. 4 is a diagrammatic axial cross sectional view of a trip valve typical of those used in the invention; and

FIG. 5 is a similar view with the parts in a different position.

The device comprises an impact or hammer head element 2, slidable in a tubular frame 4 in position to strike against a shank or anvil 6 slidable in relation to tube 4, in the present embodiment in a smaller tube 8 fixed in tube 4 as a guide for shank 6, and to which any suitable tool may be secured in well-known manner. A pin 10 is carried in shank 6 and slides in slots 12 in tube 4 to retain shank 6 in tube 8 while allowing limited movement. Hammer element or head 2 is urged in the direction of shank 6 by a resilient element, in this embodiment a heavy spring 14 compressed between it and an abutment 16 fixed in tubular frame 4 so that hammer 2 can be forced into powerful impacting contact with shank 6 after being pulled away by fluid pressure as will appear.

Fluid under pressure comes in through a pipe or hose 18, controlled by a well-known type of throttle valve 20, and, when permitted by the latter, passes on to a pressure-sensitive trip valve 22 which will be further described and thence through a passageway 24 in abutment 16 into a first expansible rubber or rubberlike bag or air spring 26 having an upper plate 27, and which expands upwardly, as seen in FIG. 2, and carries a pad 28 into sealing relation with the under side of a plate 30 fixed as a closure to the upper end of tube 4. A rod 32 extends, preferably axially, through bag 26, slidably through abutment 16, and through spring 14, and is permanently connected to hammer 2 preferably in a special manner as will be described, fluid leakage about rod 32 being inconsequential or prevented in any well-known manner.

With pad 28 seated against plate 30, pressure in bag 26 will increase and overcome a back-pressure valve generally designated as 34 which, in the present position of the parts projects through an opening 36 in plate 30, into the interior of a larger air spring 28. Air spring 38 expands against a washer 40, FIG. 1, in contact with a rubber or rubber-like washer 42 which, through a washer 44 and nut 46 raises rod 32. Such movement of rod 32 raises hammer 2 against the downward pressure of spring 14.

As spring 14 is compressed its resistance to further compression increases and the fluid pressure necessary to continue the compression increases and, when the fluid pressure reaches a predetermined value, valve 22 trips, as will be described, and exhausts itself and air spring 26. Air spring 38, however, is still inflated at the previous high pressure, and which pressure, through holes 48, pressing downwardly on pad 28 pushes it quickly away from plate 30, as seen in FIG. 3, the fluid in air spring 38 suddenly exhausting through holes 48, past pad 28 and escaping through exhaust ports 50 in the sides of tube 4. The aggregate cross sectional area of holes 48 is sufficient that air spring 38 is exhausted virtually instantly so that there is no serious resistance to spring 14 as it propels hammer 2 into impact with shank 6.

The sudden loss of pressure in air spring 26 and valve 22 causes the latter to trip back to its starting position, whereupon the cycle repeats itself.

Valve 22 is a commercial product, but will be described in order to set forth a complete operative mechanism.

As best seen in FIGS. 4 and 5 it comprises an elongated generally cylindrical body portion 52 having an axial bore 54 in which is slidable a fluid-tight shuttle valve generally designated as 56 comprising spaced piston portions 58 and 60 connected by a stem portion 62, the hole being urged toward the right in FIG. 4 by a spring 64. In the position of the parts in FIG. 4 pressure fluid enters through an inlet 66, passing between pistons 58 and 60 to an outlet portion 68 and thence to above mentioned passageway 24, seen in FIGS. 1, 2 and 3. An exhaust port 70 leading out of bore 54, in this position of the parts is blocked by piston 58. The pressure building up in outlet 68 is also transmitted through a passageway 72 to a relief valve 74 maintained in a closed or seated position by a spring 76, the force of which may be adjusted by a screw 78. At some point determined by the adjustment of screw 78 the pressure will build up to a point sufficient to unseat valve 74 whereupon fluid will flow through a passageway 80 leading to the end of bore 54 to the right of piston 60 so as to overcome spring 64 and shift shuttle valve 56 to the left, as seen in FIG. 5. Piston 60 then blocks inlet 66 while piston 58 opens bore 54 to exhaust passageway 70 so that passageway 68, and therefore passageway 24 is suddenly relieved of pressure. In order for the cycle to repeat, the fluid trapped in bore 54 to the right of piston 60 is exhausted through hereinbefore mentioned passageway 80 and a non-return, or check valve 82 back to passageway 68, valve 82 being seated by a very light spring 83. At this instant, passageway 68, and therefore passageway 80, is connected to exhaust passageway 70, whereupon spring 64 will quickly return shuttle valve 62 to starting position so that the action will repeat itself. The space to the left of piston 58 is vented through a port 82 to avoid blocking the movement of shuttle valve 62.

It is desirable that the last described tripping of valve 22 be delayed a fraction of a second so that hammer 2 will have time to deliver its blow to shank 6 before air spring 38 begins to inflate again, and for this purpose a valve 84 is provided which may be turned by appropriate external means to partially block passageway 72. In this way the return of shuttle valve 62 may be delayed as much as desired, and which will determine the frequency of the hammer blows.

The force of the blows may be adjusting screw 78 which, as stated, will control the pressure at which valve 74 will be unseated, and accordingly the pressure in passageways 68 and 24, and therefore the degree of compression of spring 14 at the time air spring 38 is suddenly exhausted, and the movement of hammer 2 toward impact with shank 6 is started.

Fluid passing to trip valve 22 may be controlled in various ways, but in the illustrative embodiment hereinbefore described throttle valve 20 is supported on housing 4 as seen in FIG. 1 and supplied with pressure fluid through above mentioned pipe or hose 18. Valve 20 has a stem 86 which when pressed permits flow of fluid from pipe 18 into inlet pipe 66 of valve 22. A connection in the form of a rod 88 is slidable in a sheath 90 fixed on housing 4 and extends into proximity to a portion of pin 10 projecting from housing 4 such that shifting of pin 10 upwardly, when a tool carried by shank 6 is pressed against its work, will shift rod 88 in sheath 90 and press an offset portion 92 of rod 88 against stem 86 and open throttle valve 20 to start the hammering action.

It has been observed that the severe vibration developed in hammer 2 by the repeated blows on shank 6 will cause rapid deterioration or "fatigue" of rod 32 if the latter is fixed to hammer 2, and therefore rod 32 terminates in a well known type of coupling 94 which connects it with a length of flexible cable 96. Cable 96 extends part way through hammer 2, axially, and terminates in a swage 98 which prevents the pull of rod 32 from pulling cable 96 out of hammer 2. To protect spring 14 from severe vibration arising from the hammer blows it is seated on a washer 100 which in turn is seated on a rubber or rubber-like washer 102 which exerts a damping effect on extraneous vibrations, which would otherwise be set up in the spring by the hammer blows.

Relief valve 34 comprises a tubular body 104 best seen in FIGS. 2 and 3, fixed in and projecting above plate 27 to extend through opening 36, as stated, and having a bore 106 therethrough providing a reduced portion forming a seat 108 against which a ball valve 110 is pressed by a light spring 112 reacting against a pin or other anchorage 114.

The device will operate in any position, and a suitable handle or handles may be provided for manipulating the hammer, or, when made in larger sizes it may be mounted on a boom or the like forming part of a tractor, crane or similar device.

OPERATION.

The operation of the device is thought to be clear from the above - sufficient to say, pressing a tool against the work shifts shank 6 and pin 10, pressing rod 88 into contact with stem 86 so that valve 20 admits fluid to valve 22. The fluid passes into air spring 38 which expands and pulls rod 32 upwardly and lifts hammer 2 away from shank 6, compressing spring 14. Upon the development of a predetermined pressure in valve 22 the valve trips and exhausts air spring 26 which in turn suddenly exhausts air spring 38, allowing spring 14 to expand and drive hammer 2 into forceful contact with shank 6. The drop in pressure in valve 22 causes it to trip and again admit fluid to air spring 38, and the action repeats. The force of the blows may be regulated by adjusting the pressure of spring 76 through screw 78, and their frequency by adjusting valve 84.

Claims

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An impact tool comprising a frame including an elongated housing open at one end, a hammer element longitudinally movable within said housing, resilient means connected to said frame and to said hammer element in relation to urge said hammer element in one direction, fluid actuated means on said frame, means permanently connected with said fluid actuated means, extending to and connected in fixed relation with said hammer element in position to move said hammer element, when said fluid actuated means is activated, in the other direction, and valve means connected to said fluid actuated means and constituted to suddenly release pressure fluid from said fluid actuated means to exhaust said fluid actuated means to free said fluid actuated means and said hammer element to be propelled in the first mentioned direction by said resilient means.

2. An impact tool as defined in claim 1 in which said fluid actuated means comprises a flexible inflatable member.

3. An impact tool as defined in claim 1 in which said means connected with said fluid actuated means and with said hammer element is characterized by a section that is flexible.

4. An impact tool as defined in claim 3, said section that is flexible comprising a rod connected with said expansible member and a section of flexible wire cable permanently connected with said rod and extending to and permanently connected with said hammer head element.

5. An impact tool as defined in claim 1 in which said valve means is responsive to increase in pressure in said fluid actuated means to suddenly release pressure upon attainment of a predetermined pressure in said fluid actuated means.

6. An impact tool as defined in claim 1 in which a resilient rubber-like element is interposed between said resilient means and said hammer element for damping extraneous vibrations which would otherwise be transmitted to said resilient means.

7. An impact tool comprising a reciprocable hammer head element, a resilient element positioned to continuously urge said hammer head element in one direction, fluid pressure actuated means, valve means controlling the flow of pressure fluid into and out of said fluid pressure actuated means, means permanently connected with said fluid actuated means and extending to and connected in fixed relation with said hammer head element, said fluid actuated means comprising first and second inflatable members, said second inflatable member being connected with said means connected with said hammer head element, and having a fluid outlet, said first inflatable member being connected to receive pressure fluid from said valve means, to be inflated thereby and being positioned to seal, when inflated, said fluid outlet of said second inflatable member, said first inflatable member having means for inflating, when itself inflated, said second inflatable member, and said first inflatable member being adapted, when said valve means releases pressure fluid, to free said fluid outlet to suddenly release pressure fluid from said second inflatable member.

8. An impact tool comprising a frame including an elongated housing open at one end, a hammer head element longitudinally movable within said housing, resilient means connected to said frame and to said hammer head element in relation to urge said hammer head element in one direction, fluid actuated means on said frame, means permanently connected with said fluid actuated means extending to and connected in fixed relation with said hammer head element in position to move said hammer head element, when said fluid actuated means is activated, in the other direction, throttle valve means positioned to control the access of fluid to said fluid actuated means, a shank movably disposed in said elongated housing in position to be struck by said hammer head element when the latter is propelled by said resilient means, and connections on said housing activated by movement of said shank toward said hammer head element to actuate said throttle valve means to control the flow of pressure fluid to actuate said impact tool.