US2650572A - Pneumatic drive and damping device therefor - Google Patents

Description

pi- 1, 1953 A, AMsTu'rz 2,650,572

PNEUMATIC DRIVE AND DAMPING DEVICE THEREFOR Filed July 8, 1949 j INVENTOR ATTORNEY Patented Sept. 1, 1953 PNEUMATIC DRIVE AND DAMPIN G DEVICE THEREFOR Arnold Amstutz, Baden, Switzerland, assignor to Aktiengesellschaft, Brown, Boverl & Cie, Baden,

Switzerland, a joint-stock company Application July8, 1349, Serial No. 103,648

. In Switzerland July 31, 1948 Claims.

The present invention relates to pneumatic drives for acceleration of masses in which the driving force is applied to the mass by a pneumatically operated piston, and movement of the mass is opposed by a counter loading force applied thereto in the form of a spring or weight. In cases where the piston applied accelerating force is large in relation to the opposing force, a correspondingly large amount of energy must be absorbed in slowing down the moving system towards the end of the stroke. Buffer pistons actuated by the power piston have been employed to absorb the energy after a predetermined undamped travel of the power piston but in none of the prior known arrangements has it been possible to eliminate oscillations in the moving system towards the end of the path travelled by the mass. These oscillations can prove quite harmful in many applications and particularly so when the mass under consideration is constituted by the movable contact of a compressed gas electrical power switch and oscillation of the contact causes it to bounce with respect to the stationary contact.

The objective of the present invention is to provide an improved pneumatic drive and buffer arrangement which is practically free from oscillation. According to the invention, motion of the bufier piston is opposed by the pressure of the compressed gas applied against one side thereof. After the undamped portion of the path has been travelled by the power piston, the latter engages the other side of the buffer piston moving the same against the pressure of the compressed gas which is decreased at a uniform rate by bleeding the air to the opposite side of the buffer piston, thus bringing the mass to rest at the end of the stroke'when the pressures on the opposite faces of the buffer piston have become equalized.

In the accompanying drawings Fig. 1 is a vertical section one embodiment of the improved pneumatic drive and buffer system with the operating components shown in the positions occupied at the beginning of the stroke;

Fig. 2 is a fragmentary vertical section showing the operating components at the end of the stroke;

Fig. 3 is a vertical section of a pneumatic drive illustrating a modified embodiment of the invention; and e Fig. 4 is a view similar to Fig.2 showing the operating components of Fig. 3 at an intermediate point in the stroke. H

Referring now to the drawings and Figs. 1 and 2 in particular, themass to be moved pneumatically over the path H against the influence of a compression spring H), in overcoming the friction applied by the leaf member II is indicated generically by the block 12. The pneumatic drive is comprised of a power cylinder 13 having vents I4 at the upper end thereof leading to atmosphere, a power piston 15 slidable within cylinder 13 and including an upper section 15a of reduced diameter, and a piston rod l6 extending upwardly through a buffer or brake cylinder ll located atop the power cylinder l3 and coupled to the mass l2. The buffer piston [8 in cylinder I! includes a central aperture I80. large enough to permit free, sliding movement of the piston rod 16 and a small passageway lBb, leading from one face thereof to the other to permit the air pressures on both sides of the piston to become equalized during the braking action of the moving system.

A compressed gas such as air for operating the drive is supplied through a conduit [9 having one branch l9a in communication with the lower end of power cylinder l3 below piston I5 and another branch l9b in communication with the upper end of buffer cylinder I! above buiier piston I 8. Finally the upper end wall I3a of the power cylinder I3 is provided with a central aperture [3b large enough to pass the reduced diameter portion 15a so that the latter will engage and apply an upward force against the buffer piston I 8 after moving through the dis tance a. The stroke of the butter piston is indi cated by B in Fig. 2.

The manner of operation should now be apparent. With the components initially in the positions shown in Fig. 1, compressed air is admitted through conduit l9 causing power piston l5 to move without buffer action over the distance a. At this point the reduced portion Ilia engages the lower face of buffer piston l 8 and moves the lat ter through the distance B against a uniformly decreasing opposing pneumatic force proportional to the pressure difference at opposite sides of the buffer piston I8. Preferably the size of the aperture l8b is so chosen that the gas pressures on both sides of the buffer piston become equalized at the same instant the power piston I 5 reaches the end of its stroke as shown in Fig. 2, i. e. upon contact with the upper end wall of cylinder [3. In this manner the parts are brought to rest at the end of the stroke without the appearance of any disturbing oscillations whatsoever.

The modified construction illustrated in Figs. 3 and 4 operates on basically the same principle as that illustrated in Figs. 1 and 2 but provides for an additional controlled displacement of the mass following a slight pause at the close of the buffer phase of the operating stroke. In this. modification, the buffer cylinder 2! is divided into upper and lower chambers Zia, 2H) by a first buffer piston 22 which seats upon a shoulder portion 2 of cylinder 2i. Piston 22 is itself formed as a cylinder and contains a second buffer piston 23. The latter corresponds in function to buffer piston IS in the Figs. 1-2 construction and is provided with an aperture 23a leading from one side of the same to the other.

The power piston 24 and cylinder 25 are arranged in generally the same manner as in Figs.

of reduced diameter instead or" the one used in Figs. 1-2. One of these, 24a is adapted to pass through a central aperture 22a in the buffer piston 22 and engage the lower side of the second buffer piston 23. The other reduced portion 24b of the piston which is of larger diameter than portion 24a is adapted to engage the lower side of buffer piston 22 after the other buffer piston 23 has been moved through-the distance B noted in Fig. 4. The inlet conduit for the compressed gasis designated 26 and numerals 25a, 25b desigthrough the distance a at which point but; er piston 23 is picked up and displaced through distance B. The entire moving system is decelerated uniformly during the latter phase of the movement as the gas pressure in chamber 23 i. e. at the lower side'of buffer piston 23 gradually becomes equal to that in chamber 210; which is of course applied to the upper side of piston 23. When the gas pressures on both sides of buffer piston 23 become equalized, i. eat the end of the distance a plus B the movin system is simultaneously halted at which time piston section 24b will have been brought into engagement with the lower side of buffer piston 22. Fig. 4 shows the parts in this intermediate position in the stroke. All during the above sequence of events, the pressure gas will have been gradually flowing through throttle valve 2'! into the lower buffer chamber Zib and this valve is so set that the gas pressure in chamber 2lbwill still be less than that in the two upper chambers 2m and 28 at the time the latter becomes equalized and the parts have been brought temporarily to rest. Further movement of the parts is thus delayed until the difference in pressure between the gas in lower chamber 211) and that existing in chambers 2m, 23 becomes smaller than a value determined by the air pressure and diameters of the pistons at which instant the pause terminates and the parts enter the third and final phase of their stroke moving through the distance w until brought to rest upon contact of the power piston 2% with the upper end wall of cylinder 25.

In closing, it is desired to point out that the novel pneumatic drive that has been described is especially suited to applications where the gas pressure is subject to variations since the pneumatic driving force acting upon the power pis- 1-2 but the piston is provided with two portions ton and the opposing pneumatic braking force applied to the buffer piston are derived from the same pressure gas source. Hence the ratio of the two forces will remain the same irrespective of any change in the pressure of the gas.

Also while the illustrated embodiments are preferred it will be evident that various changes made in the construction and arrangement of parts Without however departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A pneumatic drive comprising a power cylinder, apower piston slidable within said cylin- --de'r,"a buffer cylinder, a buffer piston slidable within said bufier cylinder and engaged by said power piston following a predetermined undamped travel of the latter, and conduit means foradmitting compressed gas from the same source to said power and buffer cylinders at one side of the pistons therein, the compressed gas in said buii'ercylinder establishing a force on said bufier-piston-opposing movement of said power piston upon engagement therewith, and said bufier piston including throttle means effective upon initial displacement of said buffer piston by said power piston to initiate transfer of said con pressed gas at a controlled ratefrom theside thereof on which said gas is admitted to the opposite side thereof upon continued displacement of said buffer piston by said power piston thereby providing a damping force on said power piston having a progressively decreasing character- .istic, thepressures on opposite sides of said buffer piston being equalized at the end of its stroke.

2. A pneumatic drive comprising a power cylinder, a power pistonslidable within said cylinder, a buffer cylinder disposed adjacent an end wall of said power cylinder, a buffer piston slidable within said buffer cylinder, said end wall including an aperture therethrough and said power piston including aportion of reduced diameter adapted to extend through said aperture into said buffer cylinder and engage the adjacent side of said bufier piston following a. predetermined undamped travel thereof, means for admitting compressed gas into said power cylinder at the end opposite said apertured end wall and into said buffer cylinder at the side or" said bufier piston opposite to that engaged by the reduced portion of said power cylinder from a common source of compressedgas and said buiier. piston including throttle means efiective upon initial displacement of said buffer piston by said power piston to initiate a controlled rate of transfer of the compressed gas from the side thereof on which said gas is admitted to the opposite side thereof upon continued displacement of said buffer piston by said power piston thereby providing a damping force on said power piston having a progressively decreasing characteristic, the pressures onopposite sides of said buffer piston being equalized at theend of its stroke.

3. A pneumatic drive as defined in claim 3 wherein said throttle means is comprised of an aperture extending between opposite faces of said buffer piston and the portion of the face 'of said buffer piston at said aperture abuts the end wall of said buffer cylinder prior to engagement by said power piston thereby maintaining said aperture in a closed condition.

4. A pneumatic drive comprising a power cylinder, a power piston slidable within said cylinder, a buffer cylinder disposed adjacent an end wall of said power cylinder," a first bu'fi'er' piston slidable in said buffer cylinder and which occupies a position of rest intermediate the ends thereof, a second buffer piston slidable within said first bufier piston, said power piston including a pair of progressively stepped portions of reduced diameter adapted to extend through central apertures provided respectively in said end Wall and first buffer piston to engage said second and first buffer pistons in succession following a predetermined undamped travel of said power piston, a main compressed gas supply conduit, branch conduits leading therefrom in parallel to said power cylinder at the end opposite said apertured end Wall and to said buffer cylinder on the side of said second bufier piston opposite to that engaged by said power piston, said second bufier piston including throttle means extending therefrom for providing a controlled rate of transfer of the compressed gas from the side thereof on which said gas is admitted to the opposite side upon displacement by said power piston, and a third branch conduit including a gas throttling device leadin from said main conduit to said buffer cylinder on the side of said first buffer piston engaged by said power piston.

5. A pneumatic device comprising a power cylinder, a power piston slidable within said cylinder, a buffer cylinder, a buffer piston slidable Within said buffer cylinder and engaged by said power piston following a predetermined undamped travel of the latter, conduit means extending from a common source of compressed gas to said power and buffer cylinders at one side of the pistons therein, the compressed gas in said buffer cylinder establishing a force on said buifer piston opposing movement of said power piston upon engagement therewith, and throttle means effective only upon initial displacement of said buffer piston by said power piston to transfer the said compressed gas in said buffer cylinder from one side of said buffer piston to the other thereby providing a damping force having a progressively decreasing characteristic, the pressures on opposite sides of said buffer piston being equalized at the end of its stroke.

ARNOLD AMSTUTZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 244,092 Thayer July 12, 1881 899,795 Osmer Sept. 29, 1908 1,712,786 Bosserdet May 14, 1929 1,956,906 Mikaelson May 1, 1934 2,249,869 Steward July 22, 1941 2,403,338 Parsons Sept. 24, 1946 2,436,191 Timmerman, Jr. Feb. 17, 1948 2,509,472 Billeter May 30, 1950

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