GB2064671A

GB2064671A - Jack

Info

Publication number: GB2064671A
Application number: GB8016160A
Authority: GB
Original assignee: JACOTTET PAUL ETS
Current assignee: JACOTTET PAUL ETS
Priority date: 1979-11-13
Filing date: 1980-05-15
Publication date: 1981-06-17
Also published as: ES8200171A1; DE3005194A1; FR2469595A1; ES496373A0

Abstract

A jack comprising a double acting piston and cylinder controlled by a servo-valve mounted in a frame (1) connected to the cylinder heads and through which fluid flow between the cylinder ends takes place. A range of jacks of varying powers is also disclosed in which the spacing between the cylinder heads is fixed throughout the range. <IMAGE>

Description

SPECIFICATION Jack The invention relates to the manufacture of controlled jacks.

These jacks are capable of very high performances, both in frequency and in speed. But these performances make them expensive and therefore unsuitable in applications which only require low frequencies and/or low speeds.

Now there is on the market, at present, no equipment to fill this gap. To satisfy this need was the problem posed by the Applicants.

They have taken a first step in this direction, by enabling certain jacks, particularly uncontrolled jacks, to exceed, in linear speed, the barrier which originated from the heating of the joints. This was the object of their Patent No. 79 1 6204 having as its title "Lip seal with hydrostatic balancing for fluid under pressure".

This result having been achieved, it remained to solve the manufacture of series which, if they were not continuous, were at least regularly graded in power, reducing as far as possible the increase in stocks to be stored, in sufficient quantities to meet the grading of the demand.

This result has been achieved by providing component parts adapted either to cover the whole range or to satisfy the widest possible range of dimensions.

The present invention is a jack comprising a double acting piston and cylinder, a frame, preferably in the form of a bar, to which are connected both the body of the jack and a servovalve for controlling operation of the jack.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a half-section on a plane perpendicular to the axis of the jack; Fig. 2 is an axial section; Fig. 3 is a section in a plane perpendicular to the plane of Fig. 2; and Fig. 4 is a diagrammatic section in an axial plane corresponding to the section plane of Fig. 2, supplemented by a diagrammatic section of the servo-valve.

The jack illustrated is basically a double acting piston and cylinder, the cylinder having cylinder heads 3 and 4.

In Fig. 1, a base plate 1 is illustrated but on the other hand the plane of fixing the plate to one of the cylinder heads 3 is clearly seen at 2.

The second cylinder head 4 is not seen in Fig. 1 but is seen in Figs. 2 and 3.

The two cylinder heads are identical in shape and in size which is one of the features of this embodiment of the invention. Integrated in these cylinder heads are the guide bearings 5 and 6 and the sealing systems 7 and 8.

Indicated at 9 are the seals between the piston and the cylinder bore, preferably of the type described in Patent 79 1 6204. Other seals of the same type are found at 10 and 1 as well as a scraper seal 1 2 of known type, these seals sealing the piston rod.

Another feature of this embodiment of the invention is the fact that the distance between the points 1 3 and 14, that is to say the spacing between the two cylinder heads, is constant, whatever the power of the jack.

If there is added to the features already described the use of parts which are common in such jacks, such as: front strap rear strap front trunnion rear trunnion front ball-and-socket joint rear ball-and-socket joint rear base (for vertical mounting) it will be seen that it is possible to reduce to the minimum the parts to be stored, a factor which has a considerable influence on the manufacturing cost.

To facilitate the reading of the drawings, there will be added below to the description already given, the parts which do not involve any inventive activity such as: a servo-valve which is not illustrated except in Fig. 4 where it appears at 15, to show its relative position in the assembly, opposite the actual jack (16) the connections of the servo-valve to the jack are indicated at 17, 18 and 17', 18', the dispiacement pick-off is indicated at 19 and its support at 20, the chambers of the jack at 21, 22 23 is a non-magnetic rod connecting the magnetic core of the displacement pick-off to the rod of the jack 24 designates the rod of the jack, 25 the fixing of the base plate to the cylinder heads 26 designates the mounting of the servo-valve 27 the tie rod which connects the two ends 28 designates the electric point to feed the pick-off the arrow 29 symbolizes the feed of high pressure oil and the arrow 30 the return to the reservoir, at low pressure.

Claims

1. A jack comprising a double acting piston and cylinder, a frame, preferably in the form of a bar, to which are connected both the body of the jack and a servo-valve for controlling operation of the jack.

2. Ajack as claimed in claim 1, in which the exchanges of liquid between the body and the servo-valve take place through the frame.

3. Ajack as claimed in claim 1 or claim 2, in which the two cylinder heads have the same dimensions and shape for a given power.

4. A jack as claimed in any preceding claim, in which the sealing system is the same on the two ends.

5. A jack as claimed in any preceding claim, in which the sealing system of the high pressure on the rod allows a slight flow to escape which is sufficient to permit cooling of the bearing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Jack The invention relates to the manufacture of controlled jacks. These jacks are capable of very high performances, both in frequency and in speed. But these performances make them expensive and therefore unsuitable in applications which only require low frequencies and/or low speeds. Now there is on the market, at present, no equipment to fill this gap. To satisfy this need was the problem posed by the Applicants. They have taken a first step in this direction, by enabling certain jacks, particularly uncontrolled jacks, to exceed, in linear speed, the barrier which originated from the heating of the joints. This was the object of their Patent No. 79 1 6204 having as its title "Lip seal with hydrostatic balancing for fluid under pressure". This result having been achieved, it remained to solve the manufacture of series which, if they were not continuous, were at least regularly graded in power, reducing as far as possible the increase in stocks to be stored, in sufficient quantities to meet the grading of the demand. This result has been achieved by providing component parts adapted either to cover the whole range or to satisfy the widest possible range of dimensions. The present invention is a jack comprising a double acting piston and cylinder, a frame, preferably in the form of a bar, to which are connected both the body of the jack and a servovalve for controlling operation of the jack. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a half-section on a plane perpendicular to the axis of the jack; Fig. 2 is an axial section; Fig. 3 is a section in a plane perpendicular to the plane of Fig. 2; and Fig. 4 is a diagrammatic section in an axial plane corresponding to the section plane of Fig. 2, supplemented by a diagrammatic section of the servo-valve. The jack illustrated is basically a double acting piston and cylinder, the cylinder having cylinder heads 3 and 4. In Fig. 1, a base plate 1 is illustrated but on the other hand the plane of fixing the plate to one of the cylinder heads 3 is clearly seen at 2. The second cylinder head 4 is not seen in Fig. 1 but is seen in Figs. 2 and 3. The two cylinder heads are identical in shape and in size which is one of the features of this embodiment of the invention. Integrated in these cylinder heads are the guide bearings 5 and 6 and the sealing systems 7 and 8. Indicated at 9 are the seals between the piston and the cylinder bore, preferably of the type described in Patent 79 1 6204. Other seals of the same type are found at 10 and 1 as well as a scraper seal 1 2 of known type, these seals sealing the piston rod. Another feature of this embodiment of the invention is the fact that the distance between the points 1 3 and 14, that is to say the spacing between the two cylinder heads, is constant, whatever the power of the jack. If there is added to the features already described the use of parts which are common in such jacks, such as: front strap rear strap front trunnion rear trunnion front ball-and-socket joint rear ball-and-socket joint rear base (for vertical mounting) it will be seen that it is possible to reduce to the minimum the parts to be stored, a factor which has a considerable influence on the manufacturing cost. To facilitate the reading of the drawings, there will be added below to the description already given, the parts which do not involve any inventive activity such as: a servo-valve which is not illustrated except in Fig. 4 where it appears at 15, to show its relative position in the assembly, opposite the actual jack (16) the connections of the servo-valve to the jack are indicated at 17, 18 and 17', 18', the dispiacement pick-off is indicated at 19 and its support at 20, the chambers of the jack at 21, 22 23 is a non-magnetic rod connecting the magnetic core of the displacement pick-off to the rod of the jack 24 designates the rod of the jack, 25 the fixing of the base plate to the cylinder heads 26 designates the mounting of the servo-valve 27 the tie rod which connects the two ends 28 designates the electric point to feed the pick-off the arrow 29 symbolizes the feed of high pressure oil and the arrow 30 the return to the reservoir, at low pressure. Claims

6. A jack as claimed in any preceding claim, in which the bearings are capable of withstanding radiai loads, the energy generated by the friction of the rod on the bearing being evacuated by the escapes of oil.

7. A jack as claimed in any preceding claim, in which the escapes of the seal are, if necessary, taken up in the plate and evacuated through the general return orifice.

8. A jack as claimed in any preceding claim, in which the bearings receive a lubrication under pressure and are fed directly by the chambers of the jacks.

9. Ajack as claimed in any preceding claim, in which the sealing devices are mounted after the bearings to permit the lubrication thereof.

10. A jack substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

11. A range of jacks of varying powers as claimed in any preceding claim, in which the armature remains identical whatever the power of the jack.

12. A range of jacks as claimed in any of claims 1 to 11, in which the spacing between the cylinder heads remains the same whatever the power of the jack.

13. A method of making a range of jacks as claimed in claim 11 or claim 12.