Implements or apparatus for applying pushing or pulling force – Fluid pressure – Vehicle attached
Patent
1982-02-01
1984-09-18
Schmidt, Frederick R.
Implements or apparatus for applying pushing or pulling force
Fluid pressure
Vehicle attached
92 53, 92 29, B66F 324
Patent
active
044719442
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to jacks, and more particularly to single-acting telescopic jacks.
It is known that jacks of the type in question comprise a cylinder with a connection to a source of pressurised fluid, and within this cylinder a series of coaxial tubular elements which may occupy a forward position in which they extend the said cylinder, or a position retracted within the cylinder in question.
In practice the above tubular elements comprise front and rear end stroke means such that, under the action of the pressure of the fluid, the tubular element having the greatest reaction surface entrains the other elements in its stroke, followed in a similar way by an adjacent element and so on, until the said tubular elements occupy a forward position extending the said cylinder. From this forward position, the process is carried out in an inverted manner towards the retracted position in which the said elements are housed within the cylinder.
In a manner known per se the front and rear end stroke means mentioned above are in general constituted by catches provided at the ends of the tubular elements. An annular depression is thus formed between these catches and in which a catch of an adjacent element may be displaced, the adjacent element itself comprising an annular throat with two end catches for the movement of another tubular element and so on, the length of the above-mentioned annular depressions defining the stroke of the tubular element which is slidably mounted in the depressions. At present the elements in question are obtained from conventional tubes machined internally and externally over their entire length to form the depressions and consequently the catches. A technique of this type has certain drawbacks.
In the first instance, the machining operations for the tubes are long and complex; they lead furthermore to a non-negligible loss of raw material.
The overall size of telescopic jacks provided with these elements is considerable, in particular as a result of the fact that the depressions provided on the tubular elements for the movement of the catches cause a considerable spacing between the said elements.
In addition, the mechanical resistance properties of commercially available tubes at present used in the construction of the tubular elements require the use of tubes having a thickness suitable for supporting pressures which may arise within the jacks. It can therefore be seen that, in addition to the considerable overall dimensions mentioned above, the jacks are heavy as a result of the structure of the tubes used.
The present invention is designed to resolve the above-mentioned problems relating to weight and overall dimensions, whilst retaining and even substantially improving the mechanical resistance of the jack, using means which have practically no effect on the cost price.
In accordance with a characteristic feature of the invention, this result is obtained by using as the basic material for a telescopic jack and including its cylinder, tubular elements of drawn steel whose properties of mechanical resistance are substantially greater than those of conventional tubes and which do not require any further machining for the sliding portions apart from a slight finishing.
In association with these tubular elements the invention provides front and rear end stroke means designed to enable progressive extension outside of the cylinder or progressive withdrawal within the cylinder of the said elements, the said front end stroke means being characterised in that they are advantageously constituted by at least one discontinuous and elastically deformable ring which is, in a retracted position of the tubular elements, housed in a first depression provided in a first tubular element, thus enabling a minimum clearance to be obtained between this first tubular element and a second adjacent tubular element, whilst in the forward position of the said first tubular element the end stroke means is partly supported in the above-mentioned depression and partly in a second depression
REFERENCES:
patent: 3353454 (1967-11-01), Donovan
patent: 3417670 (1968-12-01), Madland
patent: 4303005 (1981-12-01), Glomski et al.
Leray Gerard
Leray Jules
Schad Steven P.
Schmidt Frederick R.
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