US3179185A

US3179185A - Demolition tool with shock attenuating means

Info

Publication number: US3179185A
Application number: US202606A
Authority: US
Inventors: O'farrell Matthew
Original assignee: Chicago Pneumatic Tool Co LLC
Current assignee: Chicago Pneumatic Tool Co LLC
Priority date: 1962-06-14
Filing date: 1962-06-14
Publication date: 1965-04-20
Anticipated expiration: 1982-04-20
Also published as: GB973139A

Description

April 20, 1965 M. ox-'ARRELL DEMOLITION TOOL WITH SHOCK ATTENUATING MEANS Filed June 14, 1962 2 Sheets-Sheet 1 /f F/G. 3

FIG. 2

United States Patent Leu 3,17,185 DEMULITIN TOUL WlTH SHCK ATTENUATNG MEANS Matthew GFarrell, Utica, NY., assigner to` Chicago Pneumatic Tool Company, New York, NEI., a corporation of New .lersey Filed June 14, 1962, Ser. No. 202,606

3 Claims. (Cl. 173-133) This invention is concerned with improvements in percussive tools, particularly manually portable tools commonly known as pavement breakers or ldemolition tools.

Such tools include a hammer piston which is pneumatically reciprocated to repeatedly pound an anvil against a work steel, the work steel having a tapered work end or peg point used for breaking up the work. At times, the work steel becomes so tightly embedded in the work as to make it extremely difficult for the operator to withdraw it. lt is common practice when this occurs for the operator to pull the entire tool slidably backward relative to the work steel, and then to operate the tool so as to jar the stuck steel loose. Often the result of such action in tools of conventional structure is damage of the tool, such as a cracked front head or breakage of associated parts. This is because the powerful impacting force of the piston that would ordinarily be transmitted through the anvil to the work steel is instead transmitted to the casing of the front head. At other times, the work steel will run out, as when it suddenly breaks through the work into soft earth or into a vacant area. Continued operation of the tool following such action is also likely to result in damage to the front head and associated parts,

since in this case the impacting force of the piston will also be transmitted to the casing of the front head instead of to the Work steel.

An object of this invention is to improve such tools so as to avoid the likelihood of damage occurring to the tool when the tool is operated to loosen stuck steel, or when the steel has run through the work.

A further object of this invention is to provide in such tools means for checking or attenuating the impacting force of the piston relative to the anvil when the usual support provided by the work steel is removed from the anvil.

A still further object of this invention is to improve these tools in such manner that when the support of the work steel is removed from the anvil, the impacting force of the piston against the anvil will be so attenuated as to eliminate the likelihood of the tool being damaged, but suilicient residual force will nevertheless be transmitted to the casing of the front head to jar a stuck steel loose when the tool is operated for the latter purpose.

The invention further lies in the particular construction and arrangement of its component parts, and also in their particular cooperative association with one another to effect the objects intended herein.

The foregoing and other objects and advantages of this invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings, wherein an embodiment of the invention is illustrated. It is to be expressly understood, however, that the drawings are for purposes of illustration and description; and they are not to be construed as dening the limits of the invention.

In the drawings:

FlG. 1 is a longitudinal section through a manually portable percussive tool embodying the invention; and it shows the tool in its normal operating condition with the peg point of the work steel pressed against the solid work or pavement;

FIG. 2 is a plan view of the elastic unit;

HG. 3 is a longitudinal section through the elastic unit;

Mice

FIG. 4 is a view to that of FIG. l', but shows the work steel stuck fast in the pavement, and further shows the anvil and work steel in their low positions relative to the casing;

FIG. 5 is a fragmentary View of the tool showing the work steel as having run through the pavement; and

FIG. 6 is a sectional view showing what takes place when the piston is reciprocated relative to the anvil in the condition of the tool shown in FIG. 4, or FIG. 5.

There is illustrated in the drawings various views of a pneumatically powered manually portable percussive tool 1li in which the invention`is embodied. The tool is of a conventional type commonly known as a pavement breaker or demolition tool. The tool includes a housing or casing 11 having a front head section 12 which is secured by the usual tie-bolts, not shown, to a piston cylinder 13. The usual back-head 9 is associated with the upper end of the piston cylinder, and includes a handle 8 for guiding the tool during its operation, or for lifting or carrying it.

A hammer piston 1d is pneumatically reciprocable in the cylinder 13 to pound an anvil l5 relative to the work steel i6. During normal operation of the tool, as will be later described, the piston is enabled, without interference, to impart its full driving force against the anvil. During other times, as will also 'be later described, attenuating means is caused to materially check the movement of th piston on its work stroke before it is permitted to strike the anvil.

The attenuating means comprises a sleeve or slide member 18 and an elastic unit or elastometerl 19. The sleeve member 1S has axial movement (FIG. 6) between a hori- Zontal upper shoulder 21 and a coned lower shoulder 22 of the casing. The sleeve is supported by the elastic unit 19 so that an upper flat shoulder 23 of the sleeve normally limits against the corresponding shoulder 21 of the casing (as in FlG. 4). The elastic unit 19 comprises (FIGS. 2 and 3) a pair of

cylindrical metal tubes

24 and 25 of different diameters, arranged one within the other in parallel spaced relation and bonded to each other by means of a strong elastic material 2d filling the space between them. The elastic material illustrated here is a strong plastic, commonly known as neoprene. The outer tube 24 is seated in an annular recess 27 of the casing; and it is restrained against relative axial movement by means of a pair of opposed annular shoulders 2d of the casing. The inner tube 25 sleeves about the central `area of the sleeve 1d, and its upper end abuts an overhanging shoulder 29 of the sleeve. The sleeve 18 has an upper coned central surface 31 which is adapted to be struck at certain times by a complementary coned undersurtace 32 of the piston as the latter reciprocates. When this occurs, the sleeve 13 is forced or slid downward against the yielding resistance of the elastic unit 19 to engage a coned bottom end 33 thereof against the annular shoulder 22 of the casing, as appears in FIG. 6. As the sleeve moves downward, it carries the inner tube 25 of the elastic unit with it, causing the elastic element 26 to elastically deform downward. Such action of the piston against the sleeve will materially check or absorb the downward driving force of the piston. When the sleeve 13 is relieved of the stress or impacting force of the piston, as when the piston moves upwardly or away on its return stroke, the sleeve is returned to normal position (FIG. 4 as the elastic element` 26 naturally restores. The sheer strength of the elastic element is so computed that it will have absorbed about half the energy imparted by the piston to the sleeve 18 when the latter is stopped by the shoulder 22.

The anvil l5 has limited axial movement relative to the sleeve member 18. The anvil is guided in thismovernent by means of an enlarged lower body portion 3d thereof which bears against the adjacent wall of the sleeve; and it is further guided by means of a reduced upper elongated stem portion 35 which bears against a reduced inner annular surface 3d of the sleeve. The anvil has an elevated or normal operating position (FIG. l) in which a'coned shoulder 37 thereof limits against a complementary shoulder 38 of the sleeve, and in which the stem 35 projects in part out of and above the sleeve into the piston cylinder 13. rfhe anvil has a low or relaxed position (FIG. 4) in which a coned undersurface 3% thereof seats upon a complementary shoulder il of the casing; and in which a fiat top end d2 of the stem 35 is positioned a short distance below the lowermost edge 43 of the coned upper surface 3l of the sleeve. The low position of the anvil relative to the -sleeve i8 is such that the sleeve must rst be moved downwardly a little by the impacting action of the piston, as appears in FIG. 6, before the tlat bottom end de of the piston can strike the opposed end v adapted to engage the work. The work is here illustrated as a concrete pavement dil. A tail portion it? of the work steel is axially slidable in a stationary bushing 5l of the casing. A lange portion 52 of the work steel has limited movement below the bushing in an enlarged area 53 of the casing. A lug or stop Se, carried by the casing and projecting radially into the path of movement of the flange 52B, not only prevents endwise escape of the Work steel from the front head of the tool, but also cooperates with the rlange to determine the lowermost position of the work steel relative to the casing.

The work steel has an elevated position, as indicated in PEG. 1, during normal operation of the tool. in this situation the peg point 47 presses against the solid pavement d8, so that the tail portion C@ of the worl; steel is elevated in the bushing 5l relative to the casing. ln its elevated position, the rear portion of the work steel projects axially out of the bushing beyond the annular shoulder il of the casing; and the fiat top end 553 of the worli steel presses upwardly against the bottom end 5d of the anvil to hold the anvil raised in its elevated pcsition. Thus, the top end 42 of the elevated anvil pro'ec into the piston cylinder, and the coned undersurlace of the anvil is clear of the casing shoulder lll. Accordingly, as the piston i4 reciprocates, its full impacting force is imparted to the anvil l5 and transmitted through the latter to the work steel. As the work steel digs intoV the pavement, the front head l2 of the tool has equal downward relative movement, thus enabling the work steel to continuously hold .the anvil in its elevated position y during normal operation of the tool.

At times, the work steel will become so embedded in the work, as appears in FlG. 4, that the operator is nuable to withdraw it. When this occurs, the operator pulls back on the handle S so as to slide or draw the entire toolby means of the bushing 51 rearwardly relative to the stuck work steel until the flange 52 of the latter abuts against the stop lug 54. When the operator does this, the tail end 55 of the work steel will have a position in the bushing 5l as in FlG. 4, below the shoulder il of the casing and clear of the bottom end 56 of the anvil. The anvil, which gravitationally follows the downward relative movement of the work steel as the casing is pulled back, will seat upon the shoulder lll of the casing. The piston is then reciprocated or operated while the tool is thus held by the operator. As the piston reciprocates, its impacting force will be largely checked by the attenuating means in the manner earlier described. ln this operation of the tool a jarring action will be imparted to the casing as the sleeve liti impinges on the shoulder 22 and as the anvil receives the residual impacting force of the piston. This jarring action is insufficient to crac-li or otherwise damage the casing of the tool, its front l?. or associated parts; but it functions to cause the operator to recoil and transmit through the stop lug 5d and flange 52 to the work steel a sutlicient and necessary rearwardly acting force to jar the latter loose from its stuck condition in the pavement fili.

At other times, the work steel will suddenly run through the work into soft earth or into a vacant area below, as in FIG. 5. When this occurs, the entire tool by its own weight and under the pressing force being exerted by the operator upon the handle follows the sudden dropping action of the work steel until the bottom end 46 of the casing abuts the hard pavement. When this occurs, the anvil l5 and the work steel 1.6 will have dropped to their low positions, 'which will be the san e as that shown in FG. 4. No advantage is to be gained by operating the tool in this situation. But, the operator is not always able to immediately stop the action or the reciprocating piston under these circumstances so that the piston may continue to reciprocate for another cycle or so before he does stop it. However, the d ving force of the piston will be largely attenuated by attenuating means, as earlier described, and no dam ge will oscar to the casing or the associated parts of the tool should such further cycling of the piston occur.

lt is to be appreciated that in either of the two situations mentioned, namely, when the work steel is stuck in the Work, and when the worlt` steel runs through the work; if the full force of the piston were directed to the anvil while the latter is unsupported by the work steel and while the anvil rests upon the shoulder fil of the casing, the latter and its associating parts would very likely be cracked or otherwise damaged. y

While an embodiment of the invention has been illustrated and described in detail, it is to be expresny understood that the invention is not limited thereto. Various changes might possibly be made in the design end arrangement of the parts without departing from the spirit and scope of the invention. it is intended, therefore, to claim the invention not only as shown and described, but also in all such forms and modifications thereof as may be reasonably construed to fall within the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. In a percussive tool including a casing, a piston cylinder having a piston reciprocating therein, an annular shoulder in the casing below the piston cylinder, an anvil axially slidable in the casing seated upon the shoulder having an impact receiving face extending into the piston cylinder for receiving impacts of the piston, an axially slidable member sleeving the anvil including an annular impact receiving surface extending into the piston cylinder in the path of movement of the piston, an annular spring unit having an outer component stationary with the casing and having an axially yieldable inner component slceving the slidable member, an offset shoulder about the slidable member resting atop the said yieldable inner component, the yicldable inner component.V supporting the slidable member relative to the anvil wherein the impact receiving surface is normally slightly elevated relative to the striking face of the anvil while the anvil is seated upon said annular shoulder, and the casing having a second annular internal shoulder coaxial with and ,located radially beyond and upwardly of the rst mentioned annular shoulder; ith which second annular shoulder the axially slidable member is engageable against the resistance of the yieldable component under impact of the piston on a downward stroke of the latter, and upon such engagement the impact receiving surface of the slidable member assuming a temporary position slightly below the impact receiving face of the anvil enabling the piston upon further movement on its downward stroke to then pound the anvil against the first annular shoulder with a residual force.

2. In a percussive tool as in claim l, wherein a work steel axially slidable in the lower end of the casing has an elevated position supporting the anvil above the rst mentioned annular shoulder so that the striking face of the anvil is disposed in the piston cylinder above the impact receiving surface of the slidable member, and wherein the casing has an internal abutment and the work steel has a peripheral collar arrested by the abutment in a low position of the work steel in which low position the anvil is seated upon the rst internal shoulder of the casing and is clear of the work steel.

3. In a percussive tool of the character described ncluding a casing having an internal shoulder and a hammer piston reciprocating in the casing; means for transmitting an attenuated driving force of the piston to the internal shoulder so as to provide a controlled vibratory action to the casing without danger of cracking the casing, comprising an outer metal sleeve restrained in the wall of the casing against axial movement, an inner sleeve of reduced diameter arranged within and in parallel spaced relation to the outer sleeve and the wall of the casing, elastic material filling the space between the sleeves and bonding them to one another, an annular iloating slide member sleeved about its central area by the said inner sleeve and having an upper peripheral shoulder resting atop the inner sleeve, the slide member presenting an impact receiving face in the path of the piston, and the slide member under impact of the piston being movable into impacting engagement with the internal shoulder against the yielding resistance of the elastic material so as to translate the driving force of the piston against the slide member into a reduced torce against the internal shoulder of the casing.

4. A percussive pavement breaking tool including a casing, an anvil, a reciprocating piston, and a work steel therein, the work steel therein subject to being axially and directly pounded by the anvil Within the casing which anvil is subject to the pounding of the piston, the Work steel having a slidable relation to the casing and adapted under some conditions during operation of the tool to be substantially slidably displaced relative to the casing, shoulder means integral with the casing for disabling the anvil under such conditions from directly pounding the Work steel and for receiving the pounding of the anvil; and means in said casing in sliding relationship with said anvil to attenuate the pounding of the piston against the anvil and as a consequence against the casing during the time that the anvil is disabled from directly pounding the work steel.

5. A percussive pavement breaking tool as in claim 4, including stop means carried by the casing below the shoulder means having cooperation with the work steel for limiting the extent of such displacement and translating subsequent pounding of the anvil against the shoulder means into a recoil force of the operator against the work steel.

6. In a percussive tool of the character described including a drill steel having a flange thereon and subject Cil to becoming stuck at times in the work, a casing having an internal shoulder and a stop lug below the internal shoulder, the casing being axially slidable by manual force relative to the drill steel in an upward direction when the latter is thus stuck so as to carry the stop lug on the casing against the underside of the flange of the drill steel and so as to carry the internal shoulder of the casing to an upward position upwardly from the drill steel; an anvil axially slidable in the casing above the internal shoulder normally functioning to pound the drill steel at a point above the internal shoulder but having a position seated upon the internal shoulder when the casing is slid upwardly as above mentioned; a hammer piston reciprocable in the casing normally functioning during reciprocable movement to pound the anvil against the work steel when the anvil is not in seated position; means in said casing in sliding relation with said anvil disabling the hammer piston in its reciprocating movement from pounding the anvil with its full force while the anvil is in said seated condition so as to avoid cracking the casing but allowing the piston to pound the anvil with an attenuated force insuliicient to crack the casing.

7. ln a percussive tool according to claim 6, wherein the disabling means comprises a metal sleeve surrounding the anvil and yieldable means coaxial with the sleeve supporting the latter in a normal condition wherein an impact receiving face at the upper end of the sleeve subject to being struck by the hammer piston is below the plane of the impact receiving end of the anvil whereby the hammer piston is blocked from striking the sleeve when the anvil is in its position normally functioning to pound the drill steel, but wherein the said impact receiving end of the sleeve is above the plane of the impact receiving end of the anvil and subject to being struck by the hammer piston when the anvil is in its said seated position.

8. In a percussive tool according to claim 7, wherein the casing has a second internal shoulder of larger internal diameter than the rst and above the latter, the lower end of the sleeve is normally above and clear of the said second internal shoulder, but is subject to engaging the latter against the resistance of the yieldable means when struck by the hammer piston.

References Cited bythe Examiner UNITED STATES PATENTS 1,609,136 11/26 Stevens 121-32 2,018,096 10/35 Schorle et al. 121-19 2,519,477 8/50 Kind 173-139 2,929,361 3/60 Reynolds et al. 173-139 3,028,841 4/ 62 Leavell 121-32 FOREIGN PATENTS 880,317 3/43 France.

954,342 12/49 France.

299,538 1/ 16 Germany.

253,772 3/48 Switzerland.

BROUGHTON G. DURHAM,.Prmary Examiner. RALPH H. BRAUNER, Examiner.

Claims

3. IN A PRECUSSIVE TOOL OF THE CHARACTER DESCRIBED INCLUDING A CASING HAVING AN INTERNAL SHOULDER AND A HAMMER PISTON RECIPROCATING IN THE CASING; MEANS FOR TRANSMITTING AN ATTENUATED DRIVING FORCE OF THE PISTON TO THE INTERNAL SHOULDER SO AS TO PROVIDE A CONTROLLED VIBRATORY ACTION TO THE CASING WITHOUT DANGER OF CRACKING THE CASING, COMPRISING AN OUTER METAL SLEEVE RESTRAINED IN THE WALL OF THE CASING AGAINST AXIAL MOVEMENT, AN INNER SLEEVE OF REDUCED DIAMETER ARRANGED WITHIN AND IN PARALLEL SPACED RELATION TO THE OUTER SLEEVE AND THE WALL OF THE CASING, ELASTIC MATERIAL FILLING THE SPACE BETWEEN THE SLEEVES AND BONDING THEM TO ONE ANOTHER, AN ANNULAR FLOATING SLIDE MEMBER SLEEVED ABOUT ITS CENTRAL AREA BY THE SAID INNER SLEEVE AND HAVING AN UPPER PERIPHERAL SHOULDER RESTING ATOP THE INNER SLEEVE, THE SLIDE MEMBER PRESENTING AND IMPACT RECEIVING FACE IN THE PATH OF THE PISTON, AND THE SLIDE MEMBER UNDER IMPACT OF THE PISTON BEING MOVABLE INTO IMPACTING ENGAGEMENT WITH THE INTERNAL SHOULDER AGAINST THE YIELDING RESISTANCE OF THE ELASTIC MATERIAL SO AS TO TRANSLATE THE DRIVING FORCE OF THE PISTON AGAINST THE SLIDE MEMBER INTO A REDUCED FORCE AGAINST THE INTERNAL SHOULDER OF THE CASING.