US2769429A

US2769429A - Hydraulic device and travel limit valve

Info

Publication number: US2769429A
Application number: US367257A
Authority: US
Inventors: Louis J Lencioni
Original assignee: Lawrence H Cook
Current assignee: LAWRENCE H COOK
Priority date: 1953-07-10
Filing date: 1953-07-10
Publication date: 1956-11-06
Anticipated expiration: 1973-11-06

Description

Nov. 6, 1956 J. LENCIONI 2,769,429

HYDRAULIC DEVICE AND TRAVEL LIMIT VALVE Filed July 10, 1953 w a 60 i 50 I I I k l 5a 5 55 INVENTOR.

ATTO/P/Vfifi United States Patent F HYDRAULIC DEVICE AND TRAVEL LIMIT VALVE Application July 10, 1953, Serial No. 367,257

1 Claim. (Cl. 12138) 7 This invention relates to a hydraulic device and has for its principal object the provision of a simple, reliable and economical travel limit valve in such device for automatically limiting the travel of the fluid pressure actuated plunger that is connected with any suitable tool or other means for doing work.

Another object of the invention is the provision of a fluid pressure actuated shear having means therein for automatically stopping the actuation of the shear at the moment it has finished a cutting operation and before any objectionable strain is put on the mechanism by reason of the force exerted by the fluid.

A still further object of the invention is the provision of a safety means in a hydraulically actuated, or fluid actuated device to prevent objectionable and injurious strains on the mechanism by reason of the fluid pressure employed to actuate the device; and a still further object of the invention is the provision of a travel limit valve that may be quickly regulated to control the degree of travel of the fluid actuated plunger in a fluid pressure actuated device.

In fluid pressure actuated shears, such as a cable cutter of the type illustrated in the drawings, it has been customary to provide a manually actuated valve for relieving the pressure in a fluid pressure actuated cylinder as soon as the cable is cut, thus insuring against excessive pressure building up, and also enabling the plunger to be returned under action of a spring. If the valve is not actuated soon enough, excessive pressure will develop, and if actuated too quickly, the cut may not be completed. A pressure relief valve is usually provided, but as such valves are dependent upon a predetermined fluid pressure beyond that required to efiect a completion of the cutting operation, an excess of pressure will still be created, assuming the valve operates 'as intended. There is always the possibility of pressure relief valves sticking or failing to operate, particularly Where they may go for long periods of time without being actuated.

With the present invention, the fluid pressure in the cylinder is automatically relieved each time the plunger makes a working stroke, and the pressure will not be relieved until such stroke is completed. In other words, the pressure variations in the cylinder have no efiect when the pressure is relieved, but such relief is dependent upon the plunger travelling a predetermined distance, and each time it travels such distance, the pressure will be relieved.

Other objects and advantages will appear in the description and in the drawings.

In the drawings,

Fig. 1 is a vertical sectional view through a fluid pressure actuated device showing the invention, the device being shown in starting position before actuation thereof.

Fig. 2 is a fragmentary sectional view showing the device at the completion of its stroke when the pressure is relieved.

Fig. 3 is a fragmentary sectional view of the invention modified for a hand operated device.

In detail, the apparatus shown is a shear for cutting 2,769,429 Patented Nov. 6, 1956 cable and the like and is shown to illustrate one application of the invention.

In thedevice or machine illustrated, a cylinder 1 is provided, having a head 2 at one end, and a plug 3 is supported within said cylinder for reciprocable movement axially of the latter.

The end of the cylinder opposite head 2 is provided with a removable head 4 that, in turn is formed with an opening for passage therethrough of an extension 5 of said plunger. This extension is pinned to a cutter blade 6 having a cutting edge 7 at its end and which blade is movable across space 8 and to between a pair of cutting blades 9. The cable to be cut is normally positioned in space 8 and when the cutting edge of blade 6 moves beyond the cutting edges of blades 9 the cut will be completed. No claim is made to the foregoing structure, all of which is shown in United States Letters Patent No. 2,384,130 of September 4, 1945.

An outer wall 12 surrounds the cylinder 1 in spaced relation thereto, and the head 2 extends past the cylinder at 13 to said wall with which it may be integral. The

end of thespace between the wall 12 and the cylinder that is opposite wall 2 is closed by wall 14. Thus a chamber 15 for oil is provided around the cylinder 2.

At the side of wall 2 (and its extension 13) that is opposite the cylinder 1 is an oil supply chamber 16 having a bottom wall in continuation of the bottom part of wall 12, and an end wall 17 in spaced opposed relation to head 2, and a top wall 18.

The lower portion of the extension 13 of head 2 is formed with an opening 20 to provide a communication between chambers 15, 16 and said chambers normally contain oil, which is omitted in the drawings for purpose of clarity.

Supported on the top wall 18 of chamber 16 is a motor 22 that is connected with a conventional pump 21, the intake of which is submerged in the oil in said chamber.

The pump outlet communicates with the space between the head 2 and the plunger 3 by pipe 23 which extends to inlet 24 in said head, and a pre-set relief valve 25 carried by head 2 also communicates with said space.

The plunger 3 is normally held adjacent to head 2 by means of a relatively heavy coil spring 26 that reacts between said plunger and the head 4. Said latter head is preferably removable, being held in position by several stud bolts 27.

As already mentioned, the plunger 3 is provided with an axial extension 5 that is integral therewith, and an axially elongated recess 28 formed in said extension opens outwardly of the plunger centrally thereof. A sleeve 29 is threadedly secured within said recess at the open end of the latter, which sleeve has a head 30 projecting from the plunger for engagement with the head 2 when the plunger is at the end of its stroke nearest said head 2.

The head 2 is formed with a discharge opening 31 which is preferably smaller than the bore in sleeve 29, but which opening is coaxial with said bore.

A rod 33 is relatively loosely positioned within the recess 28 and the bore of sleeve 29. A coil spring 34 reacts between the closed end of recess 28 andsaid rod to urge said rod outwardly of the open end of said recess. Insofar as this invention is concerned the bore in sleeve 29 is part of recess 28, but by using a sleeve, as described, its inner end provides an axially facing shoulder 35 that is directed toward the closed inner end of the recess 28.

The length of rod 33 is such that, when spring 34 is compressed and the plunger is at the end of its stroke nearest the head 2, the outer rounded end of the rod will seat against the edges of aperture 31 closing the latter. Thus rod 33 becomes a valve element and oil pumped into the space 40 between the plunger 3 and head 2 will cause the plunger to move away from said head.

'fhe spring 3 4' will retain the valve element in a positiolr closing outlet 31- astheplunger moves away from head 2, and it will hold the valve element in said position untilthe plunger: has moved to; the position immediately priorto that shown-in Fig. 2 and atwhich position the cable has been completely severed. Whensaid position has been reached, a collar or projectio n 41 onthe rod 33 will be engaged by theshoulder 35 in recess 28 and will pull the rod away fromthe discharge opening-31 therebyrelieving the pressure in charnber 41 and consequently removing any likelihood of forcing the head 4 off the cylinder or breaking or injuring any Qf-"the th parts of'the'maehi'ne. f

The cylinder 1 is formed with a secondopening'43' that, in turn, is closed by a ball 44; Ball 44'is held in position tightlycl'osingopening 43 by a rod 45. Rod

saidplunger toward saidfirst-head and said; second'head... including a portion in opPosedJrelation axially, of said cylinder to said plunger for holding; said plunger in said, cylinder, an outletin said firsthead coaxial'with'saidr 1 plunger and a valve element supported on said plunger 45 isthreaded in an opening-in wall 'lz and upon rota tin-gsaid rod manually by actuation of handle 46 the'ball 44 will be moved to permit the. oilin space 40 to pass through opening 43 intochambers 15; 16 when the pump is stopped. Spring'26 is eliectivefor forcing the oil out I of the cylinder by moving plunger 3-back to the position shown inFigL l.

From the foregoing, it will be obvious that no possible 7 damage can be caused by failure of the relief valve or a by failure of 'the'operator to open valve 44 or by failure of theaoperator. to stop the motor or; pump, since the pressure in space-.40 cannot build up beyond the degree necessary to move the plunger a distance sufiicient to open valve 33-. The rod- 33 will be called a valve or valve element since that is thefimction it performs.

a In the formof the invention as seen in Fig. 3, the rotary power actuated pump is not employed, but instead, the

plunger 50 is reciprocated manually oscillating, the han dle' 51-, thus drawing fluid from reservoir 52 through duct,

SS'pa'st check valve 54 and below said plunger upon the upstroke of the latter.

Upon the down stroke of plunger 50, the fluid is forced into duct 55 which opens into the cylindrical borev 56 in 'which the plunger or piston 58 that is connected with the;

cutting blade is reciprocable.

In the case of thepower actuated device, the pressure inlet was oflset to one sideof the discharge outlet 31, but

in the present instance the port or opening 60 at the end of duct is both the inlet and outlet and the valve element 59-(which' is identical with the element 33 of Figs. 1, 2) closes said opening.

In operation, in the case of Fig. 3, as soon as the piston or plunger 58 has been moved to the position of plunger 3 in Fig.2 no further power can be applied since the fluid will'merely move back 'andforth in duct 55 with each reciprocable movement of plunger 50, with valve 54 remaining'closed; 1 This particular form of the invention is the most commonlyemployed since the hand operated device has a more general use.

I claim:

In combination with ,a single, stationary cylinder havinga first head at one end, thereof and a plunger reciprocable'witbin said cylinder with a space between said headand saidplungerfor-liquid underpressure; a second head at the end of said c'ylinder opposite to said first head and said plunger having an extension of reduced .diameter rigid therewith slidably extending through said sec-- 6 0nd head, a spring around said extension reacting between: said plunger and said se'condhead for yieldably urging:

in axial alignment with said outlet for movement relative thereto, a spring reacting between .a portion of said.

plunger and said elemen for yieldablyurging said ele-- V V ment to a position closing said outlet during movement of said plunger to a predetermined point away'from said first head, an inlet in said first head for admitting liquid under pressure into said space, means respectively onsaid plunger and on said element movable into. engaging relation upon movement of saidplunger 'to' and; pastsaid' point for moving said element-away fromsaid outlet upon, 7

movementof said plunger past said point thereby opening said outlet, an outer wall enclosing said cylinder spaced therear ound and connected with saidfirst head and with 7 said secondhead-to provide a closed chamber for liquid around 'said cylinder, a conduit for oil communicating bep tween said cylinder and. said inlet andoutlet aportion of whichconduit comprises said chamber and said inlet said outlet, an opening formed'in said cylinder adjacent to saidhead communicating with said chamber, a valve element carried'by said outer wallmovable into. and out of position closing said last mentioned opening for vad-.

mitting. liquid from said cylinder: into said chamber; and conduit. upon. actuation .of'. said last mentioned element formovementtoopen position'and means connected with V said last. mentioned element accessible from outside said wall forimanual manipulation thereof, .said inletfand said outlet being a common opening and said first mentioned valve element. being acheck valve in said conduitadapted to be intermittently opened upon liquid pressure in said conduit being: greater than liquid pressure in said cylinder.

References Cited in the'file of this patent UNITED. STATES PATENTS Sweden Apr. 6, 1948