US3367454A

US3367454A - Hydraulic damping devices

Info

Publication number: US3367454A
Application number: US516855A
Authority: US
Inventors: Schenk Ferdinand; Scherer Charles
Original assignee: SCHWEIZ WAGONS AUFZUEGEFAB
Current assignee: SCHWEIZ WAGONS AUFZUEGEFAB; SCHWEIZERISCHE WAGONS- und AUFZUGEFABRIK AG
Priority date: 1964-12-16
Filing date: 1965-12-28
Publication date: 1968-02-06
Anticipated expiration: 1985-02-06

Description

Feb. 6, 1968 F. SCHENK ET AL 3,367,454

' HYDRAULIC DAMPING DEVICES Filed Dec/28, 1965. 2 Sheets-Sheet 1 Feb. 6, F NK ET AL 3,367,454

HYDRAULIC DAMPING DEVICES Filed Dec. 28, 1965 2 SheetsSheet :2

United States Patent 3,367,454 HYDRAULIC DAMPlNG DEVICES Ferdinand Schenk, Satigny, Geneva, and Charles Scherer,

Chatelaine, Geneva, Switzerland, assignors to Schweizerische Wagonsund Aufzugefahrik A.G., Schiieren, Zurich, Switzerland Filed Dec. 28, 1965, Ser. No. 516,855 7 Claims. (Cl. 188-96) ABSTRACT OF THE DISCLOSURE A hydraulic speed-limiter is provided which includes a piston and cylinder coupled between two elements between which relative motion is possible. The speed-limiter provides for adjustment of the speed of one of these elements relative to the other in accordance with the position of the elements with respect to one another when the movement begins. To accomplish this there is provided an element permitting the flow of fluid resulting from movement of the piston in the cylinder in a controlled manner, depending on the movement of the piston and variable in accordance with the starting position thereof. The control is effected by the adjustable positioning of a shaped piece in the opening through which fluid flow takes place. Adjustment of the position of the shaped piece in relation to such opening is resisted by a spring until a threshold value of the speed of fluid flow through the opening is exceeded.

This invention relates to a hydraulic speed-limiter of the kind comprising a cylinder divided into two variable volume chambers by a piston mounted on a rod extending through at least one of the ends of the cylinder, a conduit connecting the two chambers for liquid to pass from one chamber to the other upon relative movement between the cylinder and the piston, and a variable throttling member cooperating with the conduit to vary the flow of liquid through the latter.

Speed-limiters of this kind, of unidirectional action, are in particular used in automatic door closing devices. In a lift or elevator, for example, the time required for the automatic closure of doors has a substantial influence on the speed of operation of the lift.

Now, it has been observed that with door-closers fitted with known hydraulic speed-limiters having variable throttling members, it is extremely difiicult to adjust these devices to ensure rapid closure of the doors and to enable the latter to reach the closed position at substantially zero speed, whatever open position the doors are released at and/or whatever force is exerted on the door to bring about closure thereof. In this connection, either the doors reach substantially zero speed before the closed position thereby causing the doors to stop before reaching this closed position or causing a very slow end of run, or the doors reach substantially zero speed after the closed position thereby causing the doors to slam against their stop abutments and hence to rebound, the doors then ending their run at very low speed. These adjustment difficulties are essentially due to the fact that the throughflow cross-section of the variable throttling member is set for each position of the piston within the cylinder and does not take into account piston speed, such speed depending in particular on the force exerted by the elastic return member actuating the door-closer and on the moment of inertia of the door. Now, depending on the extent to which the door is open when released, this speed can vary substantially when passing through a particular position in the course of its closing movement. Moreover, if the door is not simply released but pushed before being released, the force due to this pushing action 3,367,454 Patented Feb. 6, 1968 adds itself to the force exerted by the elastic return member and influences the closing speed of the door over its entire run.

An object of the invention is to provide a hydraulic speed-limiter which takes into account not only the position of the piston within the cylinder but also its speed, thereby making it possible to impose on the speed a predetermined upper limit for each position of the piston and to oblige the speed of the piston to coincide with this programme-forming succession of set limiting values during its entire subsequent movement, whatever may be the instant and position at which the first coincidence occurs.

According to the present invention there is provided a hydraulic speed-limiter for limiting the relative speed of one element with respect to another, said speed-limiter comprising: a cylinder member; a movable piston member in said cylinder member and dividing the same into two chambers, each of said chambers being adapted for containing a liquid and each of said members being adapted for attachment to a respective one of said elements; a conduit connecting said chambers for allowing liquid to pass from one chamber to the other during relative movement of said members and including a cylindrical cavity, a first passage connecting one portion of said cylindrical cavity to one of said chambers and a second passage connecting another portion of said cylindrical cavity to the other of said chambers; throttle means cooperating with one of said passages to regulate liquid fiow through said conduit; control means for controlling said throttle means and including a liquid flow speed detector including a mobile body disposed in said cylindrical cavity and located between said cavity portions, said mobile body having an operative connection with said throttle means for actuation thereof and having a cross-sectional area less than the cross-section of said cylindrical cavity to define an intermediate throughflow passage permitting communication between said first and second passages, liquid flowing through said intermediate passage exe'rting on said mobile body a hydraulic force varying as a function of flow speed, and hence of relative speed between said members, said speed detector further including pre-stressed spring means adapted to exert on said mobile body a predetermined elastic force to hold said throttle means in an inoperative position as long as said hydraulic force remains less than said predetermined elastic force, thus providing said speed detector with a sensitivity threshold, and adapted to yield, when said hydraulic force exceeds said predetermined elastic force and hence said threshold, to allow displacement of said mobile body and hence actuation of said throttle means to reduce the cross-section of said one of said passages by an amount dependent on the extent to which said hydraulic force exceeds said predetermined elastic force, said control means further including adjusting means operatively connected to one of said members to modify at least one of said forces in dependence on the instantaneous relative position of said members thereby to vary said sensitivity threshold.

For a better understanding of the invention and to show how it may be carried into effect, two embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is an axial section of the first embodiment;

FIGURE 2 explains with the aid of a graph the operation of this first embodiment; and

FIGURE 3 is a partly sectional view of the second embodiment.

The hydraulic speed-limiter shown in FIGURE 1 comprises a vertical cylinder 10 divided into two variable volume chambers 11 and 12 by a piston 13 securedto a rod 14 extending through the upper end of the cylinder. The piston 13 has an elongated central body 13:: which, intermediate its ends, is rigid with a flange 13b provided with a peripheral skirt 13c cooperating with the inner surface of the cylinder 10. The body 13:: is formed with an axial cylindrical cavity 15 into the upper end of which opens the lower end of rod 14, the lower end of the cavity being closed off by a disc 16. The cavity 15 communicates on the one hand with the cylinder chamber 11 via radial passages 17 formed in the body 13a above flange 13b, and on the other hand with the cylinder chamber 12 via radial passages 18 formed in the body 13a beneath flange 13b. The cavity 15 and

passages

17 and 18 form an internal conduit connecting the cylinder chambers 11 and 12 and enabling the liquid 19, e.g. oil, contained in the cylinder to passs from one chamber to the other upon relative movement between the cylinder and the piston.

The cavity 15 is divided into two parts by a mobile disc 20 located between

passages

17 and 18 and formed at its center with a circular hole 21. The disc 20 is rendered rigid with an annular slide 22, which cooperates with the inner orifices of passages 18, by a cylindrical part 23 of reduced diameter which is formed at its base with radial ports 24. The unit formed by the disc 20, the slide 22 and the intermediate part 23 is urged downwards against disc 16 by a pre-stressed spring 25 disposed be.- tween the upper end of cavity 15 and the mobile disc 20. A needle 26, which is fixed to the center of the wall forming the lower end of cylinder and which is disposed axially thereof, extends slidably through disc 16, then extends through the hole 21 in mobile disc 20 to end in an axial bore 29 formed in the lower end portion of rod 14.

In order to explain the operation of this hydraulic speedlimiter, it will be supposed that the latter is incorporated in a device for automatically closing a lift door, the opening of such door being carried out manually.

When the door is in the closed position, the piston 13 is in its lowermost position within cylinder 10 and the slide 22 rests on disc 16. When the door is opened, piston 13 is raised and the liquid contained in the upper chamber 11 flows towards the lower chamber 12 by passing through passages 17, hole 21, ports 24 and passages 18, the latter being entirely cleared by slide 22. While passing through hole 21, the liquid exerts on the mobile disc 20 a force which adds itself to that exerted by spring 25. Thus, no movement of the unit 202223 occurs in the casing and passages 18 remain entirely clear. The liquid can consequently flow from chamber 11 towards chamber 12 with a minimum of resistance, the only real resistance having to be overcome by the person opening the door being that exerted by the return spring (not shown) of the door-closer.

When the door, once opened, is released, the return spring of the door-closer tends to depress piston 13 within cylinder 10 and the liquid flows in the opposite direction, i.e. from chamber 12 towards chamber 11. When passing through the hole 21, the liquid exerts on the mobile disc a force which is opposed to that exerted by the spring 25. But, because this spring is pre-stressed and hence provides the mobile disc 20 with a sensitivity threshold, the mobile disc will only be raised by the force exerted by the liquid when this force exceeds the force exerted by spring 25. As the force exerted on the mobile disc 20 by the liquid is dependent on the pressure drop of the latter when flowing through hole 21 and as this pressure drop is in turn dependent on the throughflow passage of hole 21 and on the speed at which the liquid flows through the hole, it follows that, by reducing this throughfiow passage, a lesser flow of liquid, and hence a lesser speed of piston 13, can cause the mobile disc 20 to rise. Thus, by tying this reduction of the through flow passage to the downward movement of piston 13 within cylinder 10, it is possible to establish beforehand, for each position of the piston, an upper set speed for the piston, which, as

long as it is not reached, does not give rise to any displacement of the mobile disc 20 but which, when exceeded, gives rise to an upward movement of the disc and consequently to a braking of piston 13 by actuation of slide 22 which thus diminishes the flow of liquid through the radial passages 18.

In the embodiment shown in FIGURE 1, this tying up of the throughfiow passage of hole 21 to the movement of piston 13 is achieved by means of the needle 26. As will be observed from FIGURE '1, the upper portion of needle 26, corresponding to the run that piston 13 can have in cylinder 10, has a circular cross-section which progressively increases downwards. Thus, as piston 13 moves down, the throughflow section of hole 21 and hence the upper set speed for each position of the piston are progressively decreased. The choice of this progression is made in accordance with a ,pre-establised arbitrary law providing a pre-determined closure, or upper set speeds, programme.

Such a programme is given, by way of example, by curve 50 in the graph of FIGURE 2. In this graph, wherein the ordinate represents the speed (V) and the abscissa represents the ditferent positions (P) of a door, ranging from the open position 0 to the closed position F,

curves

51, 52 and 53 represent the actual speeds of a door between the position in which the closing movement begins and the closed position, in three ditferent cases.

Curve 52 is that of a door which is released at the open position 0 and which is solely subjected to the action of the return spring of its closing device. The door undergoes acceleration under the action of the return spring and when the speed of the door reaches speed V at the intermediate position I such speed corresponding to the upper set speed for this position, the hydraulic force exerted on disc 20 becomes greater than that exerted by spring 25 and the disc 20 is raised to reduce the flow of liquid through passages 18 by actuation of slide 22, thus braking piston 13 and hence the door in order that curve 52 may rejoin the programme curve 50.

Curve 53 is that of a door which is released at the intermediate opening position I and which is also solely subjected to the action of the return spring of its closing device. The door undergoes the same acceleration as in the preceding case, but as piston 13 occupies a lower position within cylinder 10 and as the throughfiow passage of hole 21 in the mobile disc 20 is made smaller by needle 26, curve 53 intersects the programme curve 50 at a lower speed V which speed corresponds to the upper set speed for the intermediate position I As in the preceding case, a braking action takes place to bring curve 53 back to the programme curve 50.

Curve 51 is that of a door which, once brought to the open position 0, is pushed back by hand. This extra force adds itself to that exerted by the return spring of the closing device and causes greater door acceleration than in the previous cases. Curve 51 thus intersects the programme curve 50 at a greater speed V such speed corresponding to the upper set speed for the intermediate opening position 1 If the manual force is applied beyond this point of intersection of

curves

50 and 51, as is assumed to be the case here, the actual speed of the door can substantially exceed the set speed but the force exerted by the liquid on the mobile disc and consequently the rise of the latter and of slide 22 will be all the greater, thus causing a braking action which will be all the stronger. If the door is released at the intermediate position I after having reached a topmost speed V the speed of piston 13 is rapidly decreased. It will be observed that, due to the fact that a rapid speed decrease occurs, curve 51 recrosses curve 50 under the effect of a stabilising counter-reaction before merging with curve 50.

To avoid complete closure of passages 18 by the slide 22 under the action of violent manual force applied against the door, which closure would block piston 13 within cylinder 10 and cause possible damage, there is provided beneath passages 17 an internal circular shoulder 27 against which the mobile disc 20 can abut, thereby limiting the upwardmovement of the latter and consequently of the slide 22. Moreover, a safety valve 28 is provided in flange 13b of piston 13, which valve is intended to enable a flow of liquid from chamber 12 to chamber 11, parallel to the flow via conduit 18-15-17, when the pressure exerted by piston 13 on the liquid in chamber 12 exceeds a given value.

The hydraulic speed-limiter shown in FIGURE 3 differs from the previous speed-limiter mainly in that the conduit connecting chamber 12 to chamber 11 of cylinder 10, instead of being provided in piston 13, lies outside cylinder 10, and in that needle 26, instead of being rigid with cylinder 10, is rigid with the rod 14 of piston 13, this second difference being a consequence of the first. As the cavity 15, in which are mounted the mobile disc 20 and spring 25, no longer moves with the piston to enable disc 20 to move relatively to needle 26 in order to modify the throughfiow passage of hole 21, it is for the needle 26 to move in relation do disc 20 in order to make the required modifications of this throughfiow passage in dependence on the positions occupied by piston 13 within cylinder to establish a programme curve of upper set speeds. such as curve 50 in FIGURE 2.

Moreover, as opposed to the previous embodiment, the throttling member 22 no longer consists of a slide but of a cock mounted in passage 18 and controlled by the mobile disc 20 via a rod 23 and a lever 30 between which is hingedly mounted a rigid connecting member 31, rod 23 extending fluidtightly at 32 and 33 through the ends of cavity 15.

As for the operation of this hydraulic speed-limiter, it is substantially the same as that of the previous embodiment and will therefore not be gone into again here.

Various modifications can be made to the two above described embodiments. For example, throttling member 22 can be located on the other side of the mobile disc 20 to act on the throughfiow cross-section of passages 17; instead of actuating piston 13 it is possible to actuate cylinder 10 or both; the mobile disc 20 can be replaced by a disc which is not apertured but which has a cross-section smaller than that of cavity 15, needle 26 being replaced in this case by a tubular member having an outer surface of constant cross-section to slide along the wall of cavity and an inner surface whose cross-section varies axially to modify the throughfiow passage between the non-apertured disc and the wall of the cavity in dependence on the programme curve it is desired to have; since the function of needle 26 is to modify the point of equilibrium between the force exerted by the liquid on disc and the opposing force exerted by spring 25, which is assumed to have here a linear characteristic, in dependence on the position of piston 13 within cylinder 10 by modifying the force exerted by the liquid on disc 20 at a given speed of the liquid, it is also possible to modify the equilibrium point either by a variation of the opposing force exerted by spring 25, without modifying the force exerted by the liquid on disc 20 or by a combination of these two possibilities. When only the opposing force exerted by spring is modified, the needle 26 is replaced by a rod of constant cross-section carrying at its free end a disc against which bears spring 25. In such a case, the spring that is used has a non-linear characteristic to obtain the desired programme curve of set speeds. When both of the forces present are modified, needle 26 of varying cross-section is retained and there is secured to the free end thereof a disc against which bears spring 25. In this latter case, the spring may have either a linear or non-linear characteristic; depending on which characteristic is adopted for the spring, needle 26 will have a different cross-section to achieve a particular programme curve.

In summary, the device of the invention contains interposed in the travel of the

conduit

17, 21, 18, a threshold detector which is sensitive to the speed of fiow of the liquid in this conduit and which reacts as soon as this speed exceeds the threshold value defined by the compression of spring 25, and adjusting means capable of modifying this threshold value as a function of the position of the movable piston 13 in the cylinder 10, this modification occurring according to a law of threshold value relative to position of the movable piston which may be chosen at will. These adjustment means may act either on the section of passage of the hole 21, as by needle 26 (FIGS. 1 and 3), or on the compression of spring 25, as mentioned above. Finally, the threshold detector may be mounted either inside the movable piston 13, as is shown in FIG. 1, or outside the cylinder 10, as is shown in FIG. 3, but in either case it controls the throttle 22 by causing it to have a braking action on the fiow of liquid in the

conduit

17, 21, 18 when the speed of such fiow exceeds predetermined values.

The damping devices described and illustrated are unidirectionally acting. However, bi-directionally acting damping devices can be made in accordance with the invention.

By inserting in chamber 12 of cylinder 10 the return spring referred to above, the damping devices described and illustrated may form, in themselves, automatic door closing devices. Although, when describing their operation, reference was made to one particular application of these damping devices, it is clear that these damping devices can also have other applications, for example as feet for load-handling pallets.

What is claimed is:

1. A hydraulic speed-limiter for limiting the relative speed of one element with respect to another, said speed limiter comprising: a cylinder member; a movable piston member in said cylinder member and dividing the same into two chambers, each of said chambers being adapted for containing a liquid and each of said members being adapted for attachment to a respective one of said elements; a conduit connecting said chambers for allowing liquid to pass from one chamber to the other during relative movement of said members and including a cylindrical cavity, a first passage connecting one portion of said cylindrical cavity to one of said chambers and a second passage connecting another portion of said cylindrical cavity to the other of said chambers; throttle means cooperating with one of said passages to regulate liquid flow through said conduit; control means for controlling said throttle means and including a liquid flow speed detector including a mobile body disposed in said cylindrical cavity and located between said cavity portions, said mobile body having an operative connection with said throttle means for actuation thereof and having a crosssectional area less than the cross-section of said cylindrical cavity to define an intermediate throughfiow passage permitting communication between said first and second passages, liquid flowing through said intermediate passage exerting on said mobile body a hydraulic force varying as a function of flow speed, and hence of relative speed between said members, said speed detector further including pre-stressed spring means adapted to exert on said mobile body a predetermined elastic force to hold said throttle means in an inoperative position as long as said hydraulic force remains less than said predetermined elastic force, thus providing said speed detector with a sensitivity threshold, and adapted to yield, when said hydraulic force exceeds said predetermined elastic force and hence said threshold, to allow displacement of said mobile body and hence actuation of said throttle means to reduce the cross-section of said one of said passages by an amount dependent on the extent to which said hydraulic force exceeds said predetermined elastic force, said control means further including adjusting means operatively connected to one of said members to modify at least one of said forces in dependence on the instantaneous relative position of said members thereby to vary said sensitivity threshold.

2. A hydraulic speed-limiter as claimed in claim 1, wherein said adjusting means includes a member of varying cross-section cooperating with said mobile body to modify the cross-section of said intermediate passage in dependence on said instantaneous relative position of said cylinder and piston members and hence said hydraulic force exerted on said mobile body by liquid flowing at a given rate through said intermediate passage.

3. A hydraulic speed-limiter as claimed in claim 1, wherein said mobile body is a disc, wherein said intermediate throughfiow passage includes a hole formed in said disc, and wherein said adjusting means include an elongated shaped piece slidably extending into said cylindrical cavity and freely extending through said hole to modify the cross-section of said intermediate passage in dependence on said instantaneous relative position of said members and hence said hydraulic force exerted on said disc by liquid flowing at a given rate through said intermediate passage.

4. A hydraulic speed-limiter as claimed in claim 3, wherein said shaped piece is a needle having a crosssection which tapers over at least a portion of its length, said portion extending through said hole.

5. A hydraulic s eed-limiter as claimed in claim 1, wherein said piston member includes a hollow central portion defining said cylindrical cavity, wherein said one of said passages has an orifice opening laterally in said cylindrical cavity, wherein said throttle means includes a slide disposed in said cylindrical cavity adjacent said orifice for cooperation therewith and rigidly connected to said mobile body, and wherein said adjusting means is operatively connected to said cylinder member.

6. A hydraulic speed-limiter as claimed in claim 5, wherein said adjusting means includes an elongated shaped piece secured to said cylinder member, said elongated shaped piece extending slidably into said cylindrical cavity and extending through said intermediate passage to modify the cross-section thereof in dependence on said instantaneous relative position of said members and hence to modify said hydraulic force exerted on said mobile body by liquid flowing at a given rate through said intermediate passage.

7. A hydraulic speed-limiter as claimed in claim 1, wherein said conduit is disposed outside said cylinder member, and wherein said adjusting means is operatively connected to said piston member.

References Cited UNITED STATES PATENTS 2,363,867 11/1944 Isley.

2,516,667 7/1950 Bachman 18888 X 2,886,142 5/1959 Orshansky 188-88 X 2,934,175 4/1960 SchnitZer 188-88 X 3,003,595 10/1961 Patriquin 18888 3,215,283 11/1965 Shaver 213-43 MILTON BUCHLER, Primary Examiner.

G. E. A. HALVOSA, Assistant Examiner.