Motors: expansible chamber type – Working member position responsive motive fluid control – Working member carries part within working chamber which...
Patent
1993-08-05
1994-05-03
Look, Edward K.
Motors: expansible chamber type
Working member position responsive motive fluid control
Working member carries part within working chamber which...
91406, 91409, F15B 1522
Patent
active
053077296
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a device for stroke end cushioning and speed regulating the movement of a piston in a fluid pressure cylinder, comprising at least one pair of adjustable throttle means for throttling of the flow of fluid out from the cylinder, a first throttle means in said pair for regulating the piston speed being arranged to throttle the outflow of fluid through an outlet channel, a second throttle means in said pair for stroke end cushioning being arranged to throttle the outflow of fluid through a separate stroke end cushioning channel, and means for sealing the flow directly to the first throttle means from a cushioning chamber being formed in a certain mutual position between the cylinder end wall and the piston, forcing the outflow from said cushioning chamber to pass through the stroke end cushioning channel.
In fluid pressure cylinders and particularly cylinders for compressible fluid it is often necessary to have the possibility of controlling the piston speed. In such cylinders adjustment is normally achieved by a throttle which throttles the outflow of fluid from the outlet side of the cylinder. A cylinder with such a piston speed adjustment is previously known from GB,A,1 036 498.
Likewise it is often desired to slow down and cushion the movement of a piston and associated parts in the piston stroke ends. The reason for the desire to cushion the kinetic energy of these elements is the wish to avoid such stresses on the equipment that it would be exposed to otherwise without cushioning. A completely uncushioned piston is capable of striking onto the cylinder end wall with great mass energy forces as a result, while all the kinetic energy is cushioned by the throttling in an ideal cushioning process, so that the velocity of the piston falls down to zero when the piston reaches the cylinder end wall.
For the understanding of the complexity of the cushioning process it is pointed out that it depends on several parameters such as kinetic energy, cushioning length, motive power, friction, dead volume, i.e. the remaining volume when the piston reaches the end wall (such as cavities around sealing strips, channels etc). etc. To achieve an acceptable cushioning these parameters must be balanced to each other.
Stroke end cushioned cylinders are previously known in a number of variations, e.g. the applicants own marketed cylinder (the 170 series), which comprises a so called cushion sleeve cooperating with a recess in the piston at the stroke ends, forcing the outflowing fluid to pass a particular throttle U.S. Pat. No. 2,935,047 shows a stroke end cushioned cylinder wherein cushion sleeves on the piston cooperate with sealing strips to force the fluid flowing out to pass a throttle at the stroke end. U.S. Pat. No. 4,393,751 shows a hydraulic cylinder with stroke end cushioning, wherein two axially spaced ports in the cylinder wall lead directly to the outlet and via a throttle to the outlet respectively.
Through WO,A1,88/03609 a cylinder is further known being provided with an adjusting screw 6a for piston speed regulation and a particularly adjusting screw 13 for setting of a suitable cushioning. The provition of two separate means (adjustings screws) for setting the piston speed and the cushioning respectively, brings about, however, very time consuming setting and adjusting work if a desired speed and at the same time acceptable cushioning is to be achieved, since the setting of one of the two parameters, cushioning and piston speed, also affects the other.
It is therefore an object of the present invention to provide a practically useful equipment for the simple setting of speed and cushioning in a fluid pressure cylinder. This object is achieved with a device comprising the features as set forth in the characterizing part of claim 1.
A further object is to provide an equipment of the kind mentioned above which is simple in setting also by a not specially trained operator.
It has thus been found that if the two throttle means are adjusted simultaneously by the same adjusting element
REFERENCES:
patent: 3122063 (1964-02-01), Chorkey
patent: 3511133 (1970-05-01), Day
patent: 4455923 (1984-06-01), Muller
AB Rexroth Mecman
Look Edward K.
Lopez F. Daniel
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