US3599865A

US3599865A - Thermohydraulic control device

Info

Publication number: US3599865A
Application number: US848455A
Authority: US
Inventors: Svend Helge Kristiansen
Original assignee: Nordisk Ventilator Co
Current assignee: Novenco Building and Industry AS
Priority date: 1968-08-14
Filing date: 1969-08-08
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17
Also published as: NL6912315A; SE354714B; FR2015663A1; GB1273173A; DE1940899A1

Abstract

A thermohydraulic control device for a ventilation or air supply damper consisting of a hydraulic motor, comprising a cylinder in which a plunger piston is movably disposed, the volume of the cylinder being of such a size relative to its cross-sectional area that the cylinder can at the same time act as a temperatureresponsive element, the piston pin of the plunger piston being coupled to the damper shaft by means of a single-toothed rack and pinion wheel connection having engagement surfaces which lock the damper in the open or the closed position, respectively, when the tooth of the rack is out of engagement with the single toothspace of the tooth wheel.

Description

[Jnited States Patent 1 1 3,599,865

[72] Inventor Svend Helge Kristiansen [56] References Cited [21] A l N 225 2;" Denmark UNITED STATES PATENTS [22] 8 1969 2,08l,842 5/1937 Sharp 251/250 x [45] Patented Aug. 1 1971 3,207,438 9/1965 Huber 251/250 X [73] Assign Nordisk ventilator C0 A/S 3,463,391 8/1969 Haegens 236/49 Naestved, Denmark Primary ExaminerWilliam E. Wayner [32] Priority Aug. 14, 1968, Mar. 6, 1969 AttOrney-Sughrue, Rochwell, Mion, Zinn & Macpeak [33] Denmark [31] 3,923/68 and 1,254/69 ABSTRACT: A thermohydraulic control device for a ventilation or air supply damper consisting of a hydraulic motor, comprising a cylinder in which a plunger piston is movably disposed, the volume of thecylinder being of such a size relative to its cross-sectional area that the cylinder can at the same [54] THERMOHYDRAULIC CONTROL DEVICE time act as a temperature-responsive element, the piston pin 7 claimss Drawmg Flgs' of the plunger piston being coupled to the damper shaft by [52] U.S. Cl 236/99, means of a single-toothed rack and pinion wheel connection 98/32,236/49,25l/250 having engagement surfaces which lock the damper in the [51] Int. Cl F24f 13/08 open or the closed position, respectively, when the tooth of [50] Field of Search 236/49, 99, the rack is out of engagement with the single tooth-space of lOO, 98; 251/248, 250; 98/32, 33 the tooth wheel.

\ \XXK@ PATENTED nus] 7 I971 SHEET 1 OF 5 PATENTED AUG] 7197:

SHEET 3 [IF 5 FIG.3

ATTORNEY PATENTEUAUBIYIQH 3.599.865

SHEET UF 5 FIGA PATENTEU ms] new SHEET 5 BF 5 THERMOHYDRAULIC CONTROL DEVICE The present invention relates to a thermohydraulic control device for the temperature-responsive control of regulating dampers, particularly for the ventilation of stables, e.g. a stable fan with an extraction pipe and an injection pipe mounted concentrically therewith, which device has a liquid-filled cylinder and a plunger piston movable therein by changes in the liquid content of the cylinder, which changes are produced by fluctuations in temperature.

The known control devices of this kind comprise a hydraulic adjustment motor which is connected with a temperature sensor via a narrow tube and is of a rather complicated design. They are frequently employed in connection with central heating installations, for instance for the regulation of a radiator valve.

As a consequence of their constructional design, these known control devices are not very suitable for applications of the kind in which a significant controlling movement is required, as for instance for the control of dampers in air ducts in which it should be possible to turn the shaft of the damper over a very considerable angle, since, in such a case a great gear ratio between the piston rod of the adjustment motor and the shaft of the damper is required which, firstly, entails a certain inaccuracy in the adjustment and secondly, requires a correspondingly increased force of adjustment and which correspondingly bigger dimensions of the control device render it more expensive.

Consequently, as a rule, an electric motor is used for this purpose, as an adjustment motor and an electronic temperature-responsive control of same instead of a thermohydraulic control device.

An electric control device is, however, particularly costly, and where it is a question of controlling several uniform elements, e.g. several fans used in a stable, one will therefore forego an individual regulation and will control all of them in common by means of the same adjustment motor, the individual elements being, in a suitable manner, coupled mechanically. I

The thermohydraulic control deviceaccording to the invention is characteristic in that the volume of the cylinder is of such a dimension in relation to its diameter, that within the normal range of temperature fluctuations the change in volume of the quantity of liquid contained solely in the cylinder owing to these fluctuations, is great enough to cause a travel of the piston corresponding at least to the adjustment movement desired and preferably a considerably longer travel, and that for the conversion of the displacement of the piston into a rotation of the adjustment shaft of the damper, a single-toothed rack and pinion coupling is inserted between the shaft and a rod rigidly connected with the piston, said coupling having one tooth that is rigidly connected to the piston and a wheel having only one tooth space, said tooth having a flat surface situatedparallelto the direction of movement, which surface is in contact with a corresponding flat surface on the wheel in positions in which the tooth is not engaged with the tooth space.

By these means, a particularly simple construction is obtained, partly because temperature sensor and adjustment motor are constituted of one and the same element, and partly, on account of the specialcoupling between the adjustment shaft of the damper and the piston rod, since one-thereby avoids the complicated double cylinders. employed in the known devices, for the compensationof the expansion of the liquid at temperatures in excess of the regulating interval.

Finally, the employmentof suchza control device entails the advantage, as opposed to the usually employed electrical regulating members, that the control continues even if there is a power failure, so that the controlalso is effective against the natural draught through the ventilation.ducts occasioned by stopping the fan.

In a stablfiheatis generated by the animals therein and a loss of heat takes place through the walls and the roof of the building and since, as 'a rule, thegeneration of heat exceeds the natural loss of heat to such an extend that the temperature becomes too high, a certain amount of fresh air has to be supplied in order to maintain the desired temperature.

The control of the quantity of fresh air takes place in that the regulating device dealt with adjusts the damper to an aperture dependent on the stable temperature, i.e. that a change in the stable temperature brings about a rotation of the damper to a larger or smaller aperture, depending on whether the change in temperature constitutes a rise or a fall in the temperature.

The temperature change that is required in order to cause the damper to move from a fully closed to a fully open position must not be too small, as in such a case fluctuations occur. In order to obtain an even control, the temperature change in the stable temperature has to be of 4-5 C. in order to turn the damper from a fully open to a fully closed position.

If the control device is adjusted to maintain an intermediate stable temperature of, for instance 18 C., this means that the damper is going to be fully open for a supply of fresh air at a sensor temperature-and thereby stable temperature, of 20 C. This will be the case with a relatively high outside temperature, where a large supply of fresh air is required in order to remove the excess heat in the stable. In the case of falling outside temperature, the temperature in the stable will start to decrease. This causes the sensor temperature to fall and thereby to reduce the supply of fresh air further. The sensor will adjust the damper until a balance between the quantity of fresh air supplied and the generation of heat in the stable has been restored. This adjustment can only take place by the sensor temperature, and with it the stable temperature, having become lower. If a full turning of the damper requires a change in the sensor temperature of 5 C., a closing of the damper to e.g. 20 percent fresh air will correspond to a reduction in the sensor temperature and with it the stable temperature of 4 C., thus in the present example to 16 C.

This entails that the temperature in the stable cannot be maintained at an absolutely constant value independent of the outside temperature, however, normally this is of no importance, since it has been proved that a fall in the stable temperature from the value, at which the damper is exactlyfully open, to the value, at which the damper opening is reduced to approximately 20 percent, corresponds to a fall in the outside temperature of l5-20 C. It is therefore generally sufficient to carry out a subsequent adjustment at intervals gradually as the temperature, according to the season of the year, falls or rises.

At certain times, however, dependent on the climatic circumstances, considerable fluctuations in the outside temperature may occur within the same day. There are thus certain periods, during which a significant outside temperature drop occur, so that the stable temperature will drop a degree or two.

This is undesirable and the present invention therefore adopts measures to compensate for fluctuations in the outside temperature.

To this purpose the cylinder is, moreover, connected with an outside sensor for the variation in the quantity of liquid in the cylinder, which outdoor sensor contains a quantity of liquid constituting the fraction of the quantity of liquid in the cylinder necessary for the desired compensation.

In this manner, a drop in the outside temperature is going to bring about a reduction of the quantity of liquid in the cylinder in such-a way that a'smaller damper aperture is going to correspond to a given stable temperature than at a higher outside temperature, and one can thereby obtain a regulation to a constant stable temperature independent of the outside temperature.

In certain circumstances it may, however, be of advantage to bring about an over compensation in such a way that a falling outside temperature occasions a slight rise in the stable temperature. In this manner the temperature at night remains somewhat higher than during daytime, because the outside temperature at night, as a rule, is lower and this can often be of advantage to the health of the animals.

It is known in connection with a hydraulic temperature control to employ a sensor fitted in the outer atmosphere. In the known construction, however, it is a case of a central heating installation, in which by means of a sensor in the supply pipeline of the installation a control is effected for maintaining the supply-pipe temperature constant, while the sensor fitted in the outer atmosphere acts upon the control in such a way that the supply pipe temperature is raised when the outside temperature drops. It is thus here only a question of a control which serves to ensure that the requisite amount of heat is available, while the control of the temperature of the heated rooms has to be carried out independently of this control either manually or by means of thermocontrolled radiator valves.

In the following, a more detailed description of the invention will be made with reference to the drawing, in which FIG. 1 shows a part of an embodiment ofa thermohydraulic control device according to the invention,

FIG. 2 the connection of the device to two damper shafts for the adjustment of two symmetrical damper parts,

FIG. 3 the device shown in FIGS. 1 and 2 mounted together with a stable fan,

FIG. 4 a section after the lines IV-IV in FIG. 2, and

FIG. 5 an outdoor sensor to be used in connection with the device shown in FIG. 1.

In FIG. I an elongated cylinder I with a plunger piston 2 is shown. The cylinder 1 is at one end closed by a bottom piece 3 and at the opposite end provided with a mounting collar 4. In its central aperture a bushing 5 is disposed that forms a guide for the piston 2 and which is secured by means of a cover plate 6 which is bolted to the flange 4. In order to obtain the requisite sealing,

packings

7 and 8 are inserted between the cover plate 6 and the piston 7 and between the flange 4 and the bushing 5, respectively. On the end of the piston 2 situated closest to the bottom piece 3, a sleeve 9 is fixed and between this sleeve 9 and the bushing 5 a spiral spring 10 is inserted.

The part of the control device described above constitutes, at the same time, a hydraulic adjustment motor and a temperature sensor, in that the cylinder 1 is sufficiently long in relation to its cross section, e.g. having a length of up to 50 times its diameter, so that the variation in volume of a liquid contained in the cylinder through a temperature fluctuation within a suitable control interval can bring about the displacement of the piston 2 necessary for the desired adjustment.

The end of the piston 2 extending outside the cylinder constitutes a rack with a single tooth 11 at each side serving for the transmission of the linear movements of the piston to the adjustment movement, which is a rotary movement, in a way as shall be described in greater detail below in connection with FIG. 2.

In FIG. 1 a tube 12 is fitted in the bottom piece 3 connecting the inside of cylinder I with the inside ofa cylinder 13 with a piston 14. The piston 14 penetrates through a sleeve 15 that is screwed into the cylinder 13 and which tightens against a sealing ring 38 which produces sealing between the cylinder and the piston. The bushing 15 has an exterior thread, by means of which it is screwed into an outer cylinder 16 which, at the end situated opposite to the cylinder 13, is provided with an axial screw 17 which abuts against the end of the piston 14 and is provided with a counter nut 18. The cylinder 13 has a temperature scale 19 on its outer surface.

The unit described above connected with the cylinder via a pipeline 12 serves for the adjustment of the control device, since a displacement of the piston 14 in the cylinder 13 will bring about a change in the amount ofliquid in the cylinder 1 and by this means a corresponding movement of the piston 2. Such a displacement is brought about by the outer cylinder 16 being more or less screwed down over the cylinder 13, by which means the screw 17 rigidly connected with the cylinder 16 occasions the displacement of the piston 14.

During the assembly, an adjustment of the scale 19 is first carried-out by means of the screw 17, which is subsequently secured in the adjusted position in relation to the cylinder 16 by means of the counter nut 18.

The quantity of liquid contained in the cylinder 13 and the pipeline l2 constitutes such a small fraction of the quantity of liquid contained in the cylinder that it has no bearing upon the functioning of the control device in dependence of temperature fluctuations. By the way, it could be directly built together with the cylinder 1, since a piston corresponding to the piston 14 in an extension of the lower end of the cylinder 1 would produce the same effect, but by making use of a pipe connection, the possibility is created for fitting the adjustment unit in an easily accessible position.

FIG. 2 shows the connection between the piston 2 and two

adjustments shafts

20 and 21 for a damper with two symmetrical halves each mounted on one of the two shafts, but not shown in FIG. 2.

The connection is a rack and pinion coupling, in that the two members 23 that are fixed each on their

respective shafts

20 and 21 and constructed with a tooth space 24, with which the tooth 11 is engaged. The members 23 may therefore be regarded as tooth wheels, in which the toothing is reduced to the one tooth gap which is the only effective one, because'the rack interacting with the tooth wheels has only one single tooth.

The two single teeth and the tooth spaces are constructed in such a way that each of the two teeth precisely disengages from the corresponding tooth space in each of the two extreme positions ofthe

shafts

20 and 21,

The tips of each of the two single teeth 11 are shaped as a flat surface 22 that is parallel to the direction of movement of shaft 2.

When the temperature drops to such an extent that the teeth 11 disengage from the tooth spaces by the movement of the piston 2 into the cylinder and the damper is thus completely closed, a continued temperature drop and movement of the piston 2 will have the effect that the surfaces 22 slide along corresponding surfaces 26, adjoining the tooth spaces 24 of the two members 23 and which, in the completely closed position ofthe damper, lie parallel to the direction of movement of the piston 2. It is ensured by this means that the damper is kept quite closed also after the engagement between the teeth and the tooth spaces has ceased.

The corresponding effect is produced when the temperature rises, so that the teeth disengage to the opposite side where the damper is fully open, in that the surfaces 22 slide along surfaces 25 on the parts 23 adjoining the opposite side of the tooth spaces 24.

Since in certain cases temperatures may occur which lie considerably higher than the control interval, i.e. higher than the temperature at which the damper occupies exactly the fully open position, the members 23 are for the sake of safety provided with extensions 27, on which the surfaces 25 continue into surfaces 28, in a way that even at a very high temperature it is ensured that the damper is kept in a fully open position.

The described construction of the movement transmission mechanism is a very essential feature of the contml device as a whole, since the complicated measures which otherwise have to be taken in thermohydraulic control devices for the limitation of the movement of the piston at temperatures exceed ng the control interval, are avoided altogether, and such measures would in praxis be exceedingly difficult to carry out when the hydraulic adjustment motor and the temperature sensor are constituted of one and the same element and are to render possible a large adjustment movement within the control interval.

The parts described are disposed in a housing 29 which is bolted to the flange 4.

This housing 29 and the cylinder 1 are shown in FIG. 3, where the described control device is mounted on a stable fan.

30 denotes the uppermost part of the extraction duct of the fan and 32 the uppermost part of the injection duct fitted concentrically around same, while 33 denotes the roof cowl into which the two ducts terminate.

The two

damper parts

34 and 35 of the fan, which are mounted on the

shafts

20 and 21, are adjusted by means of the control device. The cylinder 1 of the device acting as a temperature sensor, is disposed directly in the airflow extracted from the stable, in that it is situated axially in the duct 30.

In order to reduce the adjustment force required, the damper parts are connected with

counterweights

36 and 37, respectively.

A control device like the one described may be used in an analogous manner for the adjustment of a damper having a single adjustment shaft. In such a case, it is only necessary that the guide for the piston 2 is dimensioned in such a way as to be able to absorb the radial forces which can occur, while these, on account of the symmetry in the construction described, act as equally strong forces in the opposite direction and consequently do not affect the control of the piston.

FIG. 4 shows a particularly expedient embodiment of the two members or tooth wheels 23, in that these are formed of

slats

40 and 41. Of these slats, the slats 40 are of such a shape that they form the said extensions 27 on the members 23, while the slats 41 are made without these extensions and the slats are mounted in a way that the slats 40 on the one member 23 are situated facing the slats 41 on the other member 23, viz. as seen in the drawing, in such a way that the one member consists of a bundle of slats 40 with a bundle of slats 41 on each side, and on the other one of a bundle of slats 41 with a bundle of slats 40 on each side.

By the use of such slats punched out from plates, a far simpler manufacture is achieved than by manufacturing the members from solid metal, on account of the complicated milling operation necessary in such a case.

The outside sensor shown in FIG. 5 comprises a cylinder 51 which, via a pipeline 52, is destined to be connected to the liquid-filled cylinder described, with reference to FIG. 1 which constitutes the actual control device.

ln cylinder 51 a displaceable piston 53, is fitted, in that the necessary sealing is produced by means of a sealing ring 54, which-is tightened by means of a cylindrical top piece 55 screwed on to the cylinder 51.

Into the end of the top piece 55 lying opposite to the piston, an adjustment screw 56 is screwed, which serves for the adjustment to a larger or smaller volume of the liquid in the cylinder 51.

The size of this volume depends on the influence the outside temperature is desired to have on the adjustment of the fan carried out by means of the screw.

If, for instance, it is proved that the influence of the outside temperature on the regulation in a change in the outside temperature of 20 C. corresponds to a change in the inside temperature of 4 C. and full compensation is desired, so that a drop in the outside temperature does not bring about any change in the stable temperature, it will, depending on the dimensioning of the control device, generally be sufficient that the quantity of liquid which is contained in the cylinder 51 constitutes 20-25 percent of the quantity of liquid in the control device itself.

Within certain limits, the degree of compensation can, in the embodiment shown, be adjusted by means of the screw 56 and it may thus be sometimes desirable to adjust to a certain slight overcompensation, for instance, in such a way that a temperature rise of l-2 C. occurs in the stable when there is a drop of l0 C. in the outside temperature.

In place of a construction like the one shown in FIG. 5, a simple container with a constant volume may also be used,

since the volume does not have to be adjusted with a particularly great accuracy. Also in this case, the volume of the container may be dimensioned to produce a certain overcompensation, if this is desired.

I claim:

1. A thermohydraulic control device for the temperatureresponsive control of a regulating damper comprising, a liquid-filled cylinder and a plunger piston movable in said cylinder by the expansion and contraction of the liquid content of said cylinder due to temperature fluctuations, said piston having a piston rod rigidly connected'therewith, a control shaft for said damper, coupling means being inserted between said shaft and said piston rod comprising a single tooth rack connected to said piston and a wheel having only one tooth space connected to said shaft, said tooth engaging said wheel and having an end surface, said wheel being provided with corresponding surfaces on opposite sides of said tooth space engageable with said end surface of said tooth when said tooth is moved outside said tooth space to positively maintain said shaft in the adjust position during continued movement of said piston.

2. A control device as claimed in claim 1 in which said cylinder is, moreover, connected with an outdoor sensor for the variation of the quantity of liquid in said cylinder, said outdoor sensor containing a quantity of liquid which constitutes the fraction of the quantity of liquid in said cylinder necessary for the compensation for variations of the temperature of said sensor.

3. A control device as claimed in claim 2, in which said quantity of liquid in said outdoor sensor is so great that said compensation is an over-compensation corresponding to a rise of the temperature of said cylinder of 12 C. when there is a drop in temperature of 10 1 5 C. in said sensor.

4. A control device as claimed in claim 1, in which said cylinder is provided with means for adjustment of the liquidcontaining volume of said cylinder.

5. A control device as claimed in claim 4, in which said liquid'containing volume of said cylinder is connected to a second cylinder having a second displaceable piston.

6. A thermohydraulic control device for the temperatureresponsive control of a regulating damper consisting of two symmetrical damper parts comprising, a liquid filled cylinder and a plunger piston movable in said cylinder by the expansion and contraction of the liquid content of said cylinder due to temperature fluctuations, said piston having a piston rod rigidly connected therewith, a control shaft for each of said damper parts, said control shafts being disposed parallel to each other, coupling means being inserted between said shafts and said piston rod comprising a rack having two single teeth connected to said piston and extending in opposite directions and a wheel having only one tooth space connected to each of said shafts, each of said teeth engaging a respective wheel and having an end surface, each ofsaid wheels being provided with corresponding surfaces on opposite sides of said tooth space engageable with said end surface of each tooth when said teeth are moved outside said too h spaces to positively maintain said shafts in the adjusted position during continued movement of said piston.

7. A control device as claimed in claim 6 wherein each of said wheels is comprised of a plurality of punched slats some of which are provided with elongated extensions which will cross each other in one extreme position of said piston, said elongated extensions having opposed surfaces disposed parallel to each other in the other extreme position of said piston.

Claims

1. A thermohydraulic control device for the temperatureresponsive control of a regulating damper comprising, a liquidfilled cylinder and a plunger piston movable in said cylinder by the expansion and contraction of the liquid content of said cylinder due to temperature fluctuations, said piston having a piston rod rigidly connected therewith, a control shaft for said damper, coupling means being inserted between said shaft and said piston rod comprising a single tooth rack connected to said piston and a wheel having only one tooth space connected to said shaft, said tooth engaging said wheel and having an end surface, said wheel being provided with corresponding surfaces on opposite sides of said tooth space engageable with said end surface of said tooth when said tooth is moved outside said tooth space to positively maintain said shaft in the adjust position during continued movement of said piston.

3. A control device as claimed in claim 2, in which said quantity of liquid in said outdoor sensor is so great that said compensation is an over-compensation corresponding to a rise of the temperature of said cylinder of 1*-2* C. when there is a drop in temperature of 10*-15* C. in said sensor.

4. A control device as claimed in claim 1, in which said cylinder is provided with means for adjustment of the liquid-containing volume of said cylinder.

5. A control device as claimed in claim 4, in which said liquid-containing volume of said cylinder is connected to a second cylinder having a second displaceable piston.

6. A thermohydraulic control device for the temperature-responsive control of a regulating damper consisting of two symmetrical damper parts comprising, a liquid filled cylinder and a plunger piston movable In said cylinder by the expansion and contraction of the liquid content of said cylinder due to temperature fluctuations, said piston having a piston rod rigidly connected therewith, a control shaft for each of said damper parts, said control shafts being disposed parallel to each other, coupling means being inserted between said shafts and said piston rod comprising a rack having two single teeth connected to said piston and extending in opposite directions and a wheel having only one tooth space connected to each of said shafts, each of said teeth engaging a respective wheel and having an end surface, each of said wheels being provided with corresponding surfaces on opposite sides of said tooth space engageable with said end surface of each tooth when said teeth are moved outside said tooth spaces to positively maintain said shafts in the adjusted position during continued movement of said piston.