US2400650A - Vibration apparatus - Google Patents

Description

May 21, 1946. C. LEAVELL ET AL 2,400,550

' VIBRATION APPARATUS Filed Sept. 2, 1941 2 sheets-Sheet `1 I af/esleai/ei? Jolz. Heelal' May 2l, 1946. c. LEAVELL E-rAL VIBRATION APPARATUS Filed Sept. 2, 1941 2 sheets-sheet 42 conpefssoia f 78 www;

Patented May 21, 1946 UNITED ,STATES PiirrslvrV OFFICE vIBRA'rIoN- APPARATUSl Charles Leavell, Washington, D. C., an'd John A. Wheeler, Princeton, N. J., assignors to Mechanical Research Corporation, a corporation of Pennsylvania Application September Z, 1941, zSerial No. 409,306

9 Claims.

the problem in connection with pneumatic orl other percussive tools is through the interposition of shock absorbing springs at various points between the motors of such tools and their handles. Whereassome of the vibrational forces would be dissipated in this manner, the magnitude of the objectionable forces is still appreciable, and the physical and nervous reactions upon the operators still excessive.

Pneumatic cushioning has been tried also, as disclosed for example, in the patentto Noble, 2,061,806, dated November 24, 1936, wherein an air cushion of constant volume is employed. With such construction, a relatively large proportion of the vibrational forces is nevertheless transmitted to the operator. And in the disclosures of the patents to Simpson et al., 1,221,615, dated April 3, 1917, and Faudi, 1,924,234, dated August 29, 1933, cylinder and piston structures have been interposed between the motors and their supporting handles, with.` substantially equal fluid pressures applied to opposite ends of the pistons, whereby the operator is still subjected to a large measure of the shock produced.

Springs in 'combination with fluid pressure have been proposed as wel1,.as described in the patent to Collins, 1,792,893, dated February 17,

1931, combining the advantages of these systems'.

as well as their disadvantages. 'And another prior art structure seeking to achieve the desired result appears in the patent to Benedict, 1,792,888, dated February 17, 1931, wherein there is produced at certain times, equalization of the pressures on opposite ends of the piston deiined by the housing of the' tool motor; and in this construction there will likewise be marked variations in the pressure of the entrapped air which constitutes the cushion.

The research resulting in the present invention `has led to a discovery whichis as startling due to its simplicity asv it is because of its practical importance. It has been found that if a vibratingbody (exempliiled -by a pneumatic paving breaker) is constrained to float between unequal fluid pressures of lsubstantially constant values, a constant force can be appliedto a support (handle in the case of the paving breaker) for the body which will counteract the variable `forces producing the vibration so that the vibrat- I ing body can be supported without vibratory forces reaching the support. Thus the device accomplishes the purpose of converting a vibra-4 tory recoil into a constant force.

The present invention comprises a vibratory body (such as a pneumatic tool) related to a support through relatively reciprocable elements provided with a suitable seal between them. In this manner, surfaces arranged on opposite sides of` the seal may be exposed to the requiredunequal fluid pressures of substantially constant values. During normal operation of the apparatus, one of the elements assumes a position intermediate the ends of its stroke as result of the application' of a constant force supplementing the lower fluid. pressure in opposition to the higher one.

One practical embodiment of the invention contemplates that the reciprocable elements assume the form of a cylinder and piston system.`lw

Under these conditions, packing rings may constitute the seal and the opposed pressures will be applied to the ends of the piston. One end of the piston may be exposed to atmospheric pressure under certain circumstances, while the other may be subjected to a, subatmospheric pressure. Or, one end may be exposed to superatmospheric pressure while the other is presented to atmospheric pressure. Whatever the pressure sources and values may be, they should be unequal and substantially constant. And it should be understood that the difference between these constant pressures vmay be changed in various ways to suit conditions encountered in practice. In the case of a manually operated pneumatic tool, the difference in the opposed pressures should be of such value that an operator of average size and strength by supplementing the` force of the lower pressure, can overcome the larger one to produce such relative movement of the tool and handles as to bring the piston to a position intermediate the ends of its stroke. In other applications, there will bean added force of some kind to accomplish a similar result. l

' In case a subatmospheric pressure applied to the piston or equivalent element approaches the zero pressure of a vacuum, then the more nearly a perfect vacuum is maintained, the greater will be the' effect to eliminate the transmission of` vibration to the supporting structure. In such a case it is proposed to provide an outwardly opening check valve on the corresponding cylinder end for communication with atmosphere duringV handles.

Typical applications of the invention will be understood more readily with reference to th attached drawings wherein: i

Fig. 1 is an elevation, partially in section, i1- lustrating one form of the invention;

Fig. 2 is a plan of the tool of Fig. l;

Fig. 3 is a sectional elevation illustrating a modied form of the invention;

Fig. 4 is a section taken along line .4-4 of Fig. 3; and

Fig. 5 is a section taken along line 5-5 of Fig. 3.

As depicted in Figs.- 1 and 2, a pneumatic tool 26 comprising the usual operating mechanism is supplied with compressed air through an inlet pipe 22 and is provided with a suitable exhaust port not shown. From the sides of the tool casing, two or more arms 24 project for a short distance, whereupon they are ,bent or otherwise provided with rods 26 extending longitudinally of the tool casing and carrying at their ends and the closed ends of the cylinders, despite the I volumetric variation of these chambers in operation. There will then be a. constant subatmospheric pressure (the substantially vconstant pressure of the vacuum) in these chambers maintained against constant atmospheric pressure by a constant downward force applied to the handles by the operator. y Should the operator reduce'the force applied to the handles, the piston will move downward towards the lower end of the cylinder. Reversal of the downward force applied by the operator, as by Lifting the tool by its handles, to

. move it to a new position will result in the piston moving to the extreme lower'end of its stroke due to the weight of the tool, accompanied by opening of check valve 42 should an appreciable quantity of air be entrapped in` the chamber 50. Thus, a new application of downward force to the handles will again establish the vacuum whenever desired or required.

The modication depictedfin Figs. 3, 4 and '5 is based upon somewhat similar principles, but

instead employs a superatmospheric pressure in opposition to the combination 'of atmospheric pressure and'the force of the operator applied tothe tool handles. In this case the tool 20 has been shown as having a packed upper end v 52 and an enlarged lower end 54l received in a vsuitable packed pistons 28. These pistons are reciprocably received in closely tting cylinders 30 carried by a supportingl assembly comprising a shield 3 2 andv handles 34. The pistons may be said to float in the cylinders since they vare unrestricted except for the provision of stops to prevent separation of the elements. The pneumatic tool together with its pistons and rods is Vrelatively] movable witl1.respect to the cylinder and/shield assembly. At their upper ends, the cylinders are provided with resilient b1 unpers 36 which may b e held in position by threaded spiders A38 whichprovide central bushings 39 for guiding the rods 26 and the lower ends ofthe cylinders are likewise provided with resilient bumpers 40 suitably held in position. As shown in Figs. 1 and 2 the upper ends of the cylinders are eX- posed to atmospheric pressure lwhile\the lower ends are provided with outwardly opening check valves 42 to permit the expulsion of any entrapped air when the pistons are pushed downwardly.

The admission of air from the supply pipe 22 is controlled by a valve 44 of the usual type,

By inter-` connecting the handle and the tool through such a flexible cable, there will be no interference with the relative movement of the parts.

cylinder 56 whose lower end is open to atmosphere and whose reduced upper end is closed by a cap 58. The body 60 of the tool below the packed end is shown as provided with a pair of bearing elements 6| engaging the wall of the cylinder 56, with slots 62 between them for cooperation with threaded pins'- 64 which prevent relative rotation of the'tool with respect to the cylinder and serve to impose desired limits upon the longitudinal vmovement of the tool within the cylinder. In' some cases, the ends of the pins received in the slots may be provided with soft resilient rings 66such-as rubber, for the re'duction of noise and shock. The entire casing or` cylinder 56 below the piston 52 is maintained In operation, still considering the form shown.

in Figs. 1 and 2, an operator will apply the tool to the work and bear down upon the handles Q 34 with sufcient force to move the pistons with respectto their cylinders to an intermediate position of their stroke, such as has :been depicted in Fig. 1v of the drawings. Depression of the lever 48 will then` admit air to the tool andv itsoper` ation will begin. By moving the pistons to the lpositions shown, the zero pressure of a vacuum will be approached suiciently to establish a sub- `at atmospheric pressure by suitablyventing it with slots 61 defined between webs 68.

'I'h'e supply of air in this form of the invention is delivered from a relatively large tank 68 or other source .of substantially constant pressure through a hose line. 'l0 and a port 12 into the chamber 14 dened at the upper end of the cylin-4 der between the cap 58 and piston 52. The diameters of the hose line and port are sufficiently large in relation to the diameter of said chamber so that despite movement of piston 52 in the chamber, the pressure therein will remain approximately equal to the pressure in the supply tank, and'will therefore provide a substantially constant force to be overcome at thehandles. A valve stem 'I6 projecting from the upper end of the tool is depressible by actuating the lever 48 mounted on one of the handles through a Bowden wire 46. 'I'he tank 68 is shown as receiving its supply of compressed air from a pump 18 which values to suit the tool, type of-work and operator.

Since the lower end of the cylinder is open to A atmosphere, it is required in this construction that the force applied to the handles by the operator.

stantially constant pressure in the chambers 56 defined between the lower ends of the pistons.

plus the force of atmosphere, overcome the force of the supplied air to move the piston structure to a point, intermediate its stroke such as has been depicted in Fig. 3 of the drawings.

By the expression substantially constant as applied to the forces and pressures set forth'in such a degree of constancy as will sensibly reduce vibration in a particular system to which the invention is applied, in accordance with the same principles as apply to the complete elimination cf vibration where absolutely constant values are obtainable. In those cases in which' subatmospheric pressures are used, as a perfect vacuum is approached, small pressure differences will naturally represent large pressure ratios. In order to clarify the use of terms as much as Possible, in the description and claims here involved, where substantially constant forces and pressures are alluded to, differences in such values, not ratios, are the criteria.

Whereas but two examples of the present invention h'ave been illustrated and described, it will be evident that it is applicable to many uses not specically mentioned and many forms of construction not depicted inthe drawings. The real scope of the invention will be measured therefore by the following claims.

We claim: 1. In combination with a vibratory body and a support therefor, a vibration converter comprising piston and cylinder structurerelating said body and support, means for imparting to said piston a position intermediate the ends of its tool, means providing a seal between said piston and cylinder means, and means maintaining 4the opposed ends of said piston means at unequal fluid pressures of substantially constant values, one of said pressures being atmospheric.

5. In combination with a vibratory body and a support therefon'a vibration converter compris- .ing piston and cylinder structure relating said stroke for normal operation of said body.

stroke during normal operation of said body,

means providing a. seal for said piston with respect to said cylinder, and means maintaining the opposed ends of said piston atlunequal iluid pressures of substantially constant values, one of said iiuid pressures being atmospheric.

2. In combination .with a vibratory body and a support therefor, a vibration converter comprising piston and cylinder structure relating said body and support, means for imparting to said piston a position intermediate the ends of its stroke during normal operation of said body, means providing a seal for said piston with respect to said cylinder, means for establishing iluid pressures at the ends of said cylinder, and said piston in said intermediate position having its opposed ends exposed to unequal iluid pressures of substantially constantv values, one of said fluid pressures being subatmospheric.

3. In combination with a vibratory body and a support therefor, a. vibration converter comprising piston and cylinder structure relating said body and support, means for imparting to said body and support, means providing a seal forv said piston wth'respect Ato said cylinder, means maintaining the opposed ends of said piston at unequal fluid pressureslof substantially constant values, and means for applying a force in opposition to the greater of said iluid pressures to move said cylinder and thereby to impart piston a position intermediate the ends of its one .of said pressures being atmospheric.-

6. In combination with a pneumatic toolv and v a supporting casing therefor, avibration converter comprising a housing for said tool defining a piston and a cylinder dened by said casing for reciprocably receiving said piston,

ing and thereby imparting to said tion intermediate the ends of its stroke for.nor' mal operation of said tool. piston packing for maintaining a seal between the opposite ends of Said piston, and means maintaining the opposed ends of said piston at unequal fluid pressures of substantially constant values, one of said pressures being atmospheric.

'1.- In combination with a vibratory implement and a support therefor, a device comprising a cylinder receiving a piston interconnecting said implement with its support, means for imparting to said piston a position intermediate the ends of said cylinder during operation of said implement. meansV for establishing nuid pressures-at the ends of said cylinders, said piston having an end normally exposed to atmospheric pressure,

piston a position intermediate the ends of its l stroke during normal operation of said body,

casing receiving reciprocable piston means pro-l vided by said tool, ing for moving said ing to said piston means a the ends of its stroke for normal handles carried by said cascasing and thereby impartposition intermediate operation of said means providing a seal for saidpiston with re- I mospheric.

and another enddeidning with said cylinder a chamber at subatmospheric pressure.

8. In combination with a vibratory implement and a support therefor, a vibration converter comprising piston and cylinder articulating means relating said implement and support, said cylinder having one end in constant communication with atmosphere and the other end provided with an outwardly opening relative movement oi' said piston in one direction creates a vacuum in said other end of the cylinder, and means for applying a force to said combination for creation of said vacuum.

9. In combination with a vibratory body and a support therefor, ing piston and cylinder structure body and support. said piston being freely iloating in said cylinder and a position intermediate the ends of operation of said body, means providing a seal for said piston with respect to said cylinder, and means maintaining the ton at unequal "iluid pressures ot substantially constant values, one of said pressures being at- CHARLES'LEAVEIL. 1 JOHN A.

to saidl handles y projecting from said casing for moving said casi piston a posicheck valve, whereby a vibration converter compris-4 relating saidv its stroke duringnormal

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