US2836264A - Dash-pot - Google Patents

Description

W. G RO E N DASH-POT May 27, 1958 Original Filed Jan. 14, 1953 INVENTOR: WILLEM GROEN BY ATT'YS 2,836,264 DAsn-Por Willem Groen, Chicago, 111., assignor to (insrud Machine Works, inn, Niles, lit, a corporation of Illinois Original application January 14, 1953, Serial No. 331,233,

now latent No. 2,745,320, dated May 15, 1956. Divided and this application March 6, 1956, Serial No. 569,721

3 Claims. (Cl. 188-96) This invention relates to milling machines and the like, and has particular reference to a dashpot for controlling high-speed routers and drills and other machine tools. This application is a division of my copending application, Serial Number 331,233, now Patent No. 2,745,320, granted May 15, 1956.

The main objects of this invention are to provide a dashpot which is adapted selectively to control the rate of gravitational descent of a milling head such as is shown in the said copending application and to afford relatively free elevation of the milling head; to provide an improved mechanism of this kind wherein valve means are coaxially disposed within the piston of the dashpot to adjustably meter the flow of fluid through the piston and control the rate of movement of the piston in one direction in the dashpot; to provide a movable check valve coaxially within the piston and biased to close a central port and branch ports in the piston whereby the piston is adapted to move in one direction at a controlled rate and in the other direction substantially free from resistance of fluid in said dashpot; to provide a coaxial bleed port in the check valve itself, without the necessity for separate valve structure therefore; to provide a needle valve adjustably received in coaxial relation within a piston rod of said piston for controlling the efiective diameter of said bleed port and the rate of fluid flow therethrough when the piston is moved in one direction whereby to control selectively the rate of movement of said piston in said one direction; and to provide a dashpot having coaxially disposed annular components, exceptional compactness, and relatively few parts, whereby reduced costs of manufacture and greater efficiency and uniformity of operation are obtained.

Other objects and advantages of the invention will become apparent as the description proceeds in accordance with a specific embodiment of the invention as shown in the accompanying drawings, in which:

Fig. 1 is a vertical axial section of the improved dash- P Fig. 2 is a vertical transverse section taken on line 22 of Fig. 1; and

Fig. 3 is a vertical transverse section taken on the line 33 of Fig. 1.

As set forth in my copending application, Serial Number 331,233, the dashpot of the invention is particularly adapted for use with the actuator mechanism disclosed in the said application for the purpose of controlling the gravitational descent of the milling head therein shown, although it is by no means limited to such a use. In the said copending application, the milling head is shown to be raised by a pneumatic jack which automatically retracts a piston rod with a fixed shoulder to actuate a bell crank to which the milling head is pivotally connected. The closing of a microswitch is effective to operate the pneumatic jack to move the piston rod in the other direction so as to release the bell crank, and to permit the milling head to fall by force of gravity, by

virtue of a slidable connection between the respective bell crank arm and the piston rod. By pivotally connecting an extension of the bell crank to the piston of the dashpot of the present invention, the rate of descent of the milling head is adjustably reduced, due to the compact metering means coaxially mounted in the dashpot piston. On the other hand, when itis desired to elevate the milling head, the dashpot oiiers substantially no resistance, since the check valve in which the metering orifice or bleed port is formed will then move out of sealing engagement with a relatively large central aperture in the dashpot piston and permit substantially unrestricted flow of the cushioning fiuid through the piston.

Referring now to Fig. 1, the dashpot of the present invention comprises a cylinder 32 attached to a suitable supporting structure, as by lateral gudgeons 33, and having a piston 40 slidably received therein with piston rods 31 and 41 axially connected to opposite hub extensions 42 and 42 of the piston. A head block is threadedly received on the piston rod 31, and when the dashpot is utilized in the construction shown in the aforesaid application Serial Number 331,233, the aforementioned bell crank extension is pivotally connected directly thereto.

7 As shown in Figs. 1, 2 and 3, the dashpot cylinder 32 is closed at both ends by heads 38 and 39, the piston rods 41 and 31 being slidably received therethrough in suitably sealed relationship. The piston has a main port 43 forming a relatively large passage with branch passages 44 and 44' communicating with the chamber 45 at the right side of the piston. bored on the left side of the piston 40 to form a guideway for a check valve 45 which is tapered to seat against and partly close the left-hand end of the main port 43, and the valve 45' is biased and normally urged against its seat by the spring 46. Branch ports 47 and 47' extend radially through the hub walls at the left side of the seat near the right-hand end of the valve 45'. A relatively small bleed port 48 extends axially through the a valve 45 and its effective diameter is controlled by a needle valve 49 that extends through an axial bore in the piston rod 31. An inlet port 48 in hub 42 affords access from the cylinder on the left-hand side of piston 44) to bleed port 43. The stem 50 of the needle valve 49 is adjustably connected to the rod 31 by threads 51, and has a knurled head 52 for adjusting the position of the needle valve 49 axially of the rod 31.

The cylinder 32 is normally filled with oil and its heads 38 and 39 are provided with ports 53 and 54 respectively, for injecting and removing the liquid contents of the cylinder. The port 53 is closed by plug 55 and the port 54 is closed by a valved oil cup 56.

The flow of liquid through the bleed passage 43 sets the speed at which the piston 49 can move in the left hand direction under the load that is being controlled.

This flow through the passage 48 is restricted by the needle 49, and thus can be adjusted to vary the speed of piston movement by turning the needle forward or back by the knob 52.

As shown in Fig. 1, the dashpot 32 offers practically no resistance to movement of piston 40 to the right since such movement causes the liquid to enter the passages 44 and 44' and force the valve 45' away from its seat at the left-hand end of the passage 43, thus opening that passage to the radial ports 47 and 47 and permitting a rapid flow of liquid through the piston to the left hand side thereof. Consequent relatively free and rapid movement of the piston 46 to the right is obtained.

It is to be noted that in the use of this invention shown in my said copending application, the control of the down stroke speed of the milling head when operating as a The hub 42 is counterdrill avoids the breaking of the drill when it comes through the work. Without such control a drill, on passing through the work and meeting less resistance,

-' tends to shoot through while the chip is too strong to be cut easily with the result that the'drill is often broken on? i The main advantages of this invention reside in the siinplified'form, construction, and arrangement of the dash pot and its components whereby a very simple and fool proof assembly is had, thus minimizing cost of assemblv and assuring perfect, readily regulated operation. Other advantages reside wherein all parts are of annular form and thus easily and cheaply manufactured; and in the coaxial arrangement of the parts whereby .a dashpot of very large load capacity is'had in a device of relatively small size.

. Although but onespecific embodiment of this invention is herein shown and described, it will be understood that details of the construction shown may be altered or omitted without departing from the spiritof this invention as defined by the following claims.

I claim:

1. A dashpot comprising a cylinder, a fluid in said cylinder, a piston slidably mounted in said cylinder and having a central port therethrough, said piston having a coaxial cylindrical hub extension on'eachside'thereof, one of said hub extensions having a cylindrical bore therein, a cylindrical check valve'slidably received in the bore of said one hub extension and having a conical valving tip, said valve being coaxially' biasedinto seating V engagement with the adjacent end of said central port said one hub'extension havinglateralfbranchiports-leading from said central port to said cylinderpsaid check 'valve" normally closing off communication. between Qsaid central port and said branch ports, said check valve having a bleed port extending co'axially therethrough, said one extension having afclosur e for said here atits free end' and having a lateral inlet passage communicating with said bleed port at the end of the valveopposite said tip, said central port normally communicating with the cylinder through said bleed port and inlet passage, said piston having a passage providing communicatio'nbetween said central port'and the cylinder on the other side of said piston, and the other hub extension of said piston having an adjustable needle member extending 1 axially therethrough and into said central port for regulating the eifective opening area of said check valvebleed port when said check valve isin seated position.

- 2. A dashpot comprising a cylinder, 21 fluid in said cylinder, a piston slidably mounted in said cylinder and having a central port'opening axially therethrough, said piston having a cylindrical coaxial hub extension on each side thereof, one of said hub extensions havinga cylindrical bore leading to said centralport, a check valve slidably mounted coaxially in the bore of saidione hub extension and biased into seating engagement with the adjacent end'of said central port opening, said one extensionhaving lateral branch ports providing communication between said cylinder and said central port when saidcheck valve is in opened unseated position, said in 'the construction side of, said, cylinder. andthrough said other extension into the central port opening of said piston andi'n axial alignment with the. bleedport of said check valve, and. j

check valve having a cylindrical body terminating in a conical valving tip and having a bleed port extending coaxially through the tip and body, said one extension having a laterally directed passage communicating withthe bore thereof, said central port communicating with the cylinder on the respective side of said piston through said bleed port and said inlet passage, said piston having a passage therein providing communication between said central port and the cylinder on the other side of said piston, said piston including a piston rod secured in coaxial relation to the end of the other of said hubextensions and slidably received through the corresponding having a central port opening axially therethrough, said piston having an integral hub extension on each side thereof, one of said hub extensions having an. axial bore leading to said central port and an axially movable conical check valve slidably fitted in said bore and re-,

siliently biased into seating engagement with said 'central port, said one extension having radial branch ports therein communicating. said cylinderwith saidcentral port at the valve seat end of the central port, said. radial ports being closed to'said central port by said'check .valve when. said check valve is in seated position, said check valve having a coaxial bleed port therethrough and 'said'one extension having a radial inlet passage com mu'nicating therewith, said central port normally com-' municating with the cylinder on the respective sideof sai'd piston through said bleed port and inlet passage,jsaid' piston having lateral passages therein providing communication between said central port and the cylinder on the other side of said piston, said pistonincluding a piston rod secured in coaxial relation tothe end of each of' said hub extensions and slidably received through the corresponding end Wall of said cylinder, a needle valve 2 extending coaxially through the piston rod on saidother means for adjusting said needle valve axially and rela-. tive to saidcheck valve for varying the effective area of said bleed port when said check valve is in seated position. References Cited in the file of this patent UNITED STATES PATENTS 1,455, 91

West May 15, 1923. 2,032,189 Stilling Feb. 25, '1936 2,315,531 Lucht 'Apr." 6, 1943 2,559,047

check valve is in seated Porter et a1. July 3, 19:51 1

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