US2415521A

US2415521A - Distributing valve for percussive tools

Info

Publication number: US2415521A
Application number: US547574A
Authority: US
Inventors: O'farrell Matthew
Original assignee: Chicago Pneumatic Tool Co LLC
Current assignee: Chicago Pneumatic Tool Co LLC
Priority date: 1944-08-01
Filing date: 1944-08-01
Publication date: 1947-02-11
Anticipated expiration: 1964-02-11

Description

Feb. l1, i947.

M. oFARRELq.

DISTRIBUTING VALVE FOR PERCUSSIVE TOOLS Filed Aug'. 1, 1944 www Patented Feb. 11, 1947 Unirse stares ATE? FFIQE.

DISTRIBUTING VALVE FOR PERCUSSIVE TOOLS l Application augustV 1, 1944, serial No. '547.574

This invention relates to fluid operated percussive tools such as pavement breakers, rock drills and other tools of the same general category, and more particularly to the distributing valves thereof and the arrangement of the ports and passages associated with and controlled by said distributing valves.

The main object of the invention is to provide .a pneumatic percussive tool with a distributing valvecooperating with special passages for facilitating flow of pressure fluid into the ends of the cylinder and particularly to induce, through scavenging of the front piston chamber in said cylinder, an increased acceleration of thehammer piston on its forward stroke, and thereby cause the latter to deliver a heavier striking blow to the working implement than would result from a conventional structure for this purpose.

Another object is t use but two principal moving parts, namely, the hammer piston and the distributing valve, and obtain the eicient operation of the tool solely by virtue of the form of the valve and arrangement of the fluid passages controlled thereby Without resorting to auxiliary valves or other devices.

Other objects and the advantages of the linvention will be set forth more in detail in the .following description when considered in connection with the accompanying drawing in which:

Fig. 1 is a longitudinal section of a suiiicicnt portion of a fluid operated percussive tool to embody the present invention and disclose the details thereof, both the hammer piston and distributing valve being shown in initial rear starting position;

Fig. 2 is also a partial section of the same tool showing the hammer piston at the end of the forward power stroke and the distributing valve in operated forward position for initiating the return stroke of the hammer piston; and

Fig. 3 is a section of the valve chest and distributing valve therein on an enlarged scale twice that shown in Figs. 1 and 2.

In percussive tools the eiiiciency of the Voperation obviously depends largely on the 'power and speed of the forward working strokes of the hammer piston. Especially is it important for the tool during operation to be capable of promptly expelling the spent pressure fluid from before the' hammer piston in the front piston chamber during the forward travel of said piston, because the presence of any residual fluid remaining to im'- pede or cushion the movement of the piston will denitely reduce the speed and power of the working stroke with the result that the blows dea 3 Claims'. (Cl. 121-19) livered by said hammer piston are not as powerful as to constitute eilicient use of the pressure fluid expended in operating the tool.

It is therefore now proposed to provide a percussive tool with special facilities ior quickly and thoroughly scavenging the forward piston chamber in front of the advancing hammer piston during operation so'that the pressure fluid driving the latter will cause it to accelerate in speed in the forward direction and deliver its blows to the working implement at maximum speed.

Thus in the practice of the invention, a cylinder casing It is secured upon one end of atappet bushing II against ange I2 on the latter and said bushing in turn secured to a tubular guide I3 for a working implement I4, by means of side bolts (not shown)5 the working implement being a drill steel, cutter or other implement. The cylinder casing I0 contains a slidable hammer piston I5 longitudinally reciprocable therein to strike the tappet I6 which is loosely mountedin bushing I I and adapted to transmit the impacts thus received to implement I4.

In order to drive the hammer piston, pressure fluid is conducted to the piston chamber I'I and exhausted therefrom through a special arrangement of passages as will now be explained,

Pressure uid is introduced into inlet port I8 in the rear portion t9 of the cylinder casing from a source of pressure fluid throughan air hose (not shown) and is controlled by throttle valve 20 normally held closed by spring 2I against valve seat 22 within back 4head 24 integral with grip handles 25, only a portion of the latter being shown. The rear portion I9 of the cylinder casing is secured to back head 24 by the usual side bolts (not shown). The throttle valve has a stem 2B extending through valve chamber 21 and through back head 24 to the other side of the latter so as to form a plunger projecting at its free'end into recess 28 upon the outer side vof said back head. -The latter by said recess also provides a housing for pivotallymounting the manual throttle control lever 29 on a pin or lbolt 3| in suitable position to engage against the -exposed end of the valve 'stem and depress the latter when the lever is manually depressed toward said back head, the valve stem thereby opening the valve to allow pressure fluid to enter the valve' chamber and pass into reservoir 32 through passage 33. I

A tubular valve block or valve case 34 is mounted within a counterbore .liti in cylinder casing II) and abuts against ashoulder 3S on the latter. A second hollow Valve block 3l is iitted into valve block 34 and formed with an annular peripheral recess 38 at the forward end for receiving an inwardly extending flange 39 on block 24. The inner block 31 has a rear flange 4I which lies partly in cylinder casing counterbore 35 and partly in a recess 42 in -back head 24. A resilient washer 43 is disposed between said flange and back head within the recess. Both valve blocks together form a valve chest in which a hollow distributing valve or sleeve 44 is longitudinally shiftable, while the pressure iiuid distributed and controlled by the valve reaches the latter through two groups or rows of

ports

45, 45, spaced apart in chamber 41 within valve block 31, said chamber virtually forming a continuation of the pressure fluid reservoir 32 previously mentioned.

When the distributing valve 44 occupies .the initial rear or starting position shown in Fig. 1 and the hammer piston likewise is also in its rear position, `and the operator presses lever 29 toward vbackhead 24, thereby depressing valve stem 25 and opening throttle valve 20, pressure fluid en ters valve chamber 21 and through passage 33 enters kchambers 32 and 41. From the latter chamber the iluid travels through ports 45 past the forward end 48 of the valve and through rear cylinder ports 49 into the rear portion of piston chamber I1 to impinge against the rear of hammer piston I and drive the same to` its extrem-e forward position shown in Fig.. 2. The distribut-4 ing valve is meanwhile held in its rear position by pressure uid acting on front end 4B until this effect is neutralized, as will be explained. The valve is thereafter shifted in the same direction aS that traveled by the hammer piston when the latter uncovers port, 59 (to be described), with the result that in the forward position front end 48 of said valve closely surrounds and covers the edge or shoulder 5I of the inner valve block 31 (Fig. 3) and cuts o communication between ports 45 and 49 as will also be referred to later on.

During the mentioned forward travel of the hammer Piston the residual uid in the forward portion of the piston chamber I1 in front of the piston is mostly exhausted through exhaust groove 52 and main exhaust port 53. When these are covered by the piston, the remainder of the fluid will be driven out through the forward end of passage 54 which communicates at the rear end thereof with groove 55 surrounding valve 44 in valve block 34 and then passes beneath partition 5E and over the neck 51 on the valve into exhaust groove 58 on the other side of said partition, whence the fluid escapes to atmosphere through auxiliary exhaust passage 59. The .pressure fluid continues to act against end 48 of the valve until the piston imcovers exhaust groove 52. Also during the latter stage of the forward movement of the piston, before exposing the main exhaust groove 53, said piston uncovers the forward end or opening of passage 50 which communicates at its rear end with valve flange chamber 60, allowing pressure fluid from the rear portion of the piston chamber I1 to enter said passage and chamber to exert pressure on the rear surface 6l of valve ange 62 and by virtue of its greater area than that of front end 48, overcomes the holding effect of the latter, the pressure being actually exerted on the entire rear end of valve 44 as soon as the valve has begun to move forward, with the result that valve 44. is driven forward rapidly from the position of Fig. 1 to that illustrated in Fig. 2.

As soon as the distributing valve Shifts forward, the main exhaust groove 52, opening to the atmosphere through exhaust port 53 independently releases the pressure fluid from the rear piston chamber, but as the valve then occupies the shifted forward position, the front end 48 'thereof covers edge or shoulder 5I of valve block 31 already referred to and cuts off the supply of pressure uid from chamber 41 to rear cylinder ports 49. As a result the rear portion of the piston chamber I1 largely exhausts through the main exhaust groove and port leil) However, in the forward position of the valve it no longer connects the forward portion of the piston chamber with groove 58 and auxiliary exhaust passage 59 through passage 54 and its associated groove 55 by way of valve neck 51, lbut said neck instead interconnects said groove 58 and auxiliary exhaust passage 59 with further groove 64. As groove 64 communicates through passage 65 with an intermediate part of the rear portion of the piston chamber between rear cylinder ports 49 and main exhaust groove 52, exhausting of spent fluid from said rear portion is speeded up by part of the fluid escaping throug auxiliary exhaust passage 59.

The distributing valve has a groove 65 located rearwardly of neck 51 with a plurality of holes or apertures 51 piercing the wall of said valve in said groove to the interior 59 of the valve so `as to form passages which communicate with groove 69 (Fig. 3) on an intermediate portion of inner valve block 31. Groove B9 in turn communicates through ports 46 in the latter block with the interior pressure fluid reservoir 41 within the same valve block.

In addition to the above, valve 44 has an intermediate shoulder 1I between its'greater internal diameter 68 and the smaller internal diameter 12, said shoulder cooperating with valve flange 62 during the forward shifting of the valve and forming a limited holding area eifective to hold the valve in the attained forward position by means of the pressure uid constantly present in groove 69, until the proper momeni-I for the next working stroke of the hammer piston arr1ves.

y While the valve occupies the forward position shown in Figs. 2 and 3, groove 66 on the valve communicates directly with groove 55 connected to passage 54, while apertures or ports 61 connect groove 55 with the interior reservoir or chamber 41, so that the pressure uid will be free to travel through passage 54 to the front portion of piston chamber I1 to drive the hammer piston back to the initial position shown in Fig. l. As the piston is about to return to initial position, with the valve in forward position, most of the spentv fluid in the rear of the piston chamber exhausts through groove 52 and portl 53. During the return stroke, the piston first Icovers the main exhaust groove 52 and thereafter also covers the cylinder opening of passage 50, but the remaining pressure fluid in the path of said piston in the rear portion of the piston chamber will continue to exhaust through passage 65, groove 54, valve' neck 51, groove 58 and auxiliary exhaust passage 59 until the hammer piston finally covers the forward cylinder opening of said passage 65. As the last mentioned opening is thus closed and the'A hammer piston approaches rear cylinder ports 49, the residual fluid in the path of `the pistonl becomes compressed and serves thedouble pur-.

pose of cushioning and checking the rear return;

movement of said piston, and when the pressure has become suiciently intense, of also .pressing on the front end 48 of valve 44 through ports 49 to overcome the holding force exerted by the live pressure fluid on internal holding area 1I and thereby shift said valve to its initial rear position appearing in Fig. 1 and thus complete the cycle of operation. 'Ihe apparatus is then immediately ready for a few cycle which proceeds at once to repeat the cycle just described if the pressure fluid is still supplied to the hammer piston by manually holding throttle valve open by means of lever 29.

In order to facilitate shifting of the distributing valve in both directions and to further promote escape of spent pressure uid from passage 5U, the valve flange chamber 60 is vented fore and aft to a bleeder passage 13 which connects with auxiliary exhaust passage 59, thus preventing fluid from being trapped forwardly or rearwardly of valve flange 62 in said chamber. The valve is therefore not impeded in movement by entrapped fluid but is capable of shifting abruptly and responsively under the influence of pressure uid acting through passage 50 on rear face 6| of ange 62 for forward shifting, and through rear cylinder ports 49 on the front end 48 of the valve for rearward shifting or return of said valve, resulting in correspondingly responsive and positive operation of the hammer` piston. As a further means for facilitating the rearward movement of the valve during the return stroke of the piston, the latter is provided with an annular groove 14 which connects the passage 50 with exhaust groove 52 just prior to the rearward shifting of the valve, thereby venting any residual pressure nuid in the rear part of valve flange chamber 60. It is evident from the. foregoing that the speed and the power of the blows delivered by said piston are greatly augmented by the speed of scavenging of pressure fluid from the path of movement of the valve as well as of the piston.

What is claimed is:

1. In a pneumatic percussive tool, a cylinder, a hammer piston reciprocable therein, the cylinder having a main exhaust port overrun by the piston in either direction, a valve block at the rear end of the cylinder having an internal chamber to provide a reservoir adapted to be constantly supplied with live pressure fluid, a sleeve type distributing valve encircling the valve block and arranged to reciprocate, a valve case surrounding the valve, the' valve case having a groove in constant communication with the front end of the cylinder, the valve block having two axially 6. spaced holes or rows of holes, the front end of the valve being arranged to cover and uncover the forward hole to control the supply of live air from the reservoir to the rear end of the cylinder, the valve also having apertures arranged to establish and disestablish communication between the rear hole and the groove to control the supply cf live air to the front end of the cylinder,

2. In a pneumatic percussive tool, a cylinder, a hammer piston reciprocable therein, the cylinder having a main exhaust pori'l overrun by the pis--4 ton in either direction, a valve block at the rear end of the cylinder having an internal chamber to provide a reservoir adapted to be constantly supplied with live pressure fluid, a sleeve type distributing valve encircling the valve block and arranged to reciprocate to control the distribution of pressure fluid from the reservoir to the respective ends of the cylinder, a valve case surrounding the valve, the valve case having three axially spaced annular grooves, the intermediate groove being connected to exhaust, the rear groove to the front end of the piston chamber, and the front groove to the rear portion of the cylinder, the valve having a neck portion arrangedV in one position of the valve to connect the intermediate and rear grooves to provide an auxiliary exhaust for the front end of the cylinder and in another position to connect the intermediate and front grooves together to provide an auxiliary exhaust for the rear end of the cylinder.

3. A percussive tool according to claim 2 in which the valve block and valve have perforations adapted to establish communication between the reservoir and the rear annular groove when said groove is cut off from the intermediate groove to admit live air to the front end of the cylinder.

MATTHEW OFARREIL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,017,287 Nell Oct. 15, 1935 1,636,651 Smith July 19, 1927 1,637,001 Katterjohn July 26, 1927 1,774,266 Gustafson Aug. 26, 1930 '724,736 Prindle Apr. 7, 1903