EP0328926A2 - Pressure switch - Google Patents

Abstract

The pressure switch has a switching piston (3) which can be acted on by a control spring (7) against a switching pressure. To adjust the switching pressure, the control spring is supported via a spring plate (10) against the switch housing (1), which spring plate is arranged such that it can be screwed on a threaded spindle (13). The threaded spindle (13) is supported on the switch housing (1), in an axially unmovable manner, and can be turned at random by means of a hexagonal section (15) projecting into free space. A ram (20), connected to the switching piston (3), has two individual stops (24 and 28) between which there engages the end (42) of a rotating lever (43). On the other hand, the switching ram (45) of a microswitch (46) rests on the rotating lever (43), the rotating lever (43) being spring-loaded in the switching direction of the microswitch (46). In order to adjust the switching hysteresis, the one individual stop (28) is formed by a nut (27) which can be screwed on the ram (20). The nut (27) cannot rotate and is coupled in an axially moving manner to a threaded sleeve (31) which is screwed to the switch housing (1). The screwing lifting movement of the threaded sleeve (31) is limited by stops. The threaded sleeve (31) can be rotated at random by means of a hexagonal section (34) projecting into free space. The two hexagonal sections (15 and 34) are located on opposite sides of the switch housing (1). The arrangement ensures separate adjustment, without sticking, of the switching pressure and of the switching hysteresis. <IMAGE>

Description

The invention relates to a pressure switch with adjustable switching pressure and adjustable switching hysteresis, with a switching piston acted upon by the switching pressure against the force of a control spring, with a stop device with an idle stroke, which is movable in both directions of movement and has two individual stops axially offset from one another, and with one bistable snap-action switching device switchable by the stop device, the force of the control spring being adjustable by a first adjusting screw connection and the axial distance of the individual stops being adjustable by a second adjusting screw connection.

Such pressure switches are known from a brochure "pressure switch, float switch" from Klöckner-Möller. The switching piston acts on a threaded spindle which can be rotated by means of an adjusting wheel. The control spring is supported on the switching piston side against a spring plate which is non-rotatably guided axially displaceably and screwed to the threaded spindle in an adjustable manner. One of the individual stops is fixedly arranged on the threaded spindle, while the second individual stop is formed by a nut which is adjustably screwed to the threaded spindle; the nut can be rotated by means of the setting wheel via an arbitrarily switchable coupling device. A releasable locking pin closes unwanted rotations of the setting wheel. Due to the double function of the setting wheel, incorrect settings can be made, and incorrect settings that lead to jamming are also possible.

Another shortcoming of the known pressure switches can be seen in the fact that, when installed in a control panel, the dial located on the top of the switch can hardly be operated, since it is almost inaccessible.

It is an object of the invention to design a pressure switch of the type specified at the outset with simple means in such a way that the switching pressure and the switching hysteresis can be set independently of one another by means of separate actuating elements, incorrect settings causing jamming being excluded. In addition, the pressure switch should also be suitable for a panel mounting.

This object is achieved according to the invention by designing the pressure switch according to the features known in part that
the end of the control spring facing away from the switching piston is supported adjustable against the switch housing via the first adjusting screw connection,
the switching piston carries the two individual stops on a tappet on its side facing away from the control spring,
- A rotatable part of the second adjusting screw is axially displaceable and non-rotatably coupled to a threaded sleeve adjustable with the switch housing, and
- The manually rotatable threaded sleeve can be screwed to the switch housing by only a limited stroke by means of two axial stops.

Through this design, the pressure switch receives two structurally completely separate adjustment fittings for separately adjusting the preload of the control spring and thus the switching pressure on the one hand and the axial distance of the individual stops and thus the switching hysteresis on the other hand, the adjustment of the axial distance being limited without jamming due to the stroke limitation of the threaded sleeve.

According to the further invention, the subclaims show advantageous further training options for the pressure switch. If, according to the subclaims, the sections of the threaded sleeve and the threaded spindle projecting into the open are designed as suitable profile sections, in particular hexagonal sections, they can be easily rotated from the side using a suitable tool, for example using a wrench; the adjustments can therefore be made well and precisely from the front of the pressure switch and thus also from the front of the control panel without any difficulty even when the pressure switch is installed in a control panel.

Furthermore, pressure switches are already known, in which the control spring is supported, facing away from the switching piston, against a spring plate, which is non-rotatably guided by means of a projecting nose in a longitudinal slot of the switch housing and is screwed centrally adjustable with a threaded spindle. The threaded spindle is axially immovable and rotatably supported against the switch housing in the effective direction of the control spring by an annular flange and has a profile shoulder at its end projecting into the open, which is provided with cross bores which serve to accommodate a sealing wire which can be fixed on the switch housing. The switching hysteresis of this pressure switch is not adjustable.

• Figur 1 ein Schnittbild und
• Figur 2 einen Ausschnitt aus Figur 1 in vergrößertem Maßstab.

In the drawing, an embodiment of a pressure switch designed according to the invention is shown, and shows

• Figure 1 is a sectional view and
• Figure 2 shows a detail of Figure 1 on an enlarged scale.

The pressure switch has a switch housing 1, which contains a cylinder section 2, in which a switching piston 3 is guided so as to be displaceable and sealed. On one side of the switching piston 3 there is an application chamber 4 which is connected to a line connection 5 for supplying a switching pressure. On the other hand, the switching piston 3 is adjoined by a spring chamber 6 which is acted upon by atmospheric pressure and in which there is a control spring 7 which may be composed of several individual springs. The control spring 7, which is coaxial with the switching piston 3, rests on the switching piston side on a spring plate 8 which is supported against the switching piston 3 via a ball 9 in order to compensate for spring irregularities. On the other hand, facing away from the switching piston, the control spring 7 is supported against a spring plate 10, which engages in a longitudinal slot 12 of the switch housing 1 by means of a radially projecting nose 11 and is thus guided such that it cannot be rotated axially. The spring plate 10 is screwed centrically to a threaded spindle 13 which is axially immovable and rotatably supported against the switch housing 1 in the effective direction of the control spring 7 by means of an annular flange 14. The threaded spindle 13 passes through a wall of the switch housing 1 with a cylindrical section and ends outdoors with a hexagon section 15. The hexagon section 15 is penetrated by transverse bores 16, through which a sealing wire 17 is guided, which is fixed to the switch housing 1 by means of a holder 18 .

A sealing ring 19 inserted between the ring flange 14 and the wall of the switch housing 1 prevents foreign bodies or dirt from entering the spring chamber 6.

The switching piston 3 carries a plunger 20 which extends through the pressurizing chamber 4 and, with a cylindrical section 21, slidably penetrates a wall 22 of the switch housing 1 delimiting the pressurizing chamber 4. A section 23, which also belongs to the plunger 20 and is designed as a threaded pin, is screwed into section 21, a radially projecting annular disk being clamped as a single stop 24 between the two sections 21 and 23. The section 23 is connected to the individual stop 24 for screwing it into the section 21 with a profile surface section 25, which is followed by a threaded section 26 which forms the end of the plunger 20. A nut 27 is adjustably screwed to the threaded section 26, one end face of which forms a second single stop 28 which is spaced apart from the single stop 24. The outer circumferential surface of the nut 27 is formed to form axially parallel profile surfaces, with which the nut 27 is guided on corresponding inner profile surfaces 29 in a recess 30 of a threaded sleeve 31 surrounding the nut 27 so as to be non-rotatable but axially displaceable. The profile surface section 25 of the plunger 20 can be partially immersed in a recess in the nut 27 which surrounds it with play and enables relative rotations between the section 23 and the nut 27.

The threaded sleeve 31 has a threaded section 32 with an external thread, which is separated by an annular flange 33 from a hexagonal section 34 projecting into the open. The threaded section 32 is adjustably screwed to the switch housing 1. The ring flange 33 is sealed against contamination by means of a sealing ring 35 on the switch housing 1; on the one hand he has a shoulder surface 36 of the switch housing 1 and on the other hand one through one into the Switch housing 1 inserted locking ring 37 formed shoulder surface 38 opposite. The distance between the two shoulder surfaces 36 and 38 is greater than the thickness of the ring flange 33, it determines the maximum displacement stroke of the ring flange 33 and thus limits the screw stroke for the threaded sleeve 31 relative to the switch housing 1. The hexagonal section 34, which is located outdoors, is penetrated by transverse bores 39 , one of which is penetrated by a sealing wire 41 held on the switch housing 1 by means of a holder 40.

Between the two individual stops 24 and 28, one end 42 of a rotary lever 43 engages, which is rotatably mounted on the switch housing 1 in its central region. The end 42 forms, together with the two individual stops 24 and 28, a stop device 24, 28, 42. At the other end 44 of the rotary lever 43 there is a switching plunger 45 of a conventional microswitch 46. The microswitch 46 has a normal switching behavior: for switching, the switching plunger 45 must be pressed in against a certain spring force; after a certain pushing-in stroke, the microswitch 46 snaps into its switched position, the spring force loading the switching plunger 45 in its pushing-out direction being suddenly reduced significantly; when the switching plunger is released, the reduced spring force pushes it out of the microswitch 46, the microswitch 46 snapping back into its unswitched switching position and increasing the spring load of the switching plunger 45 to the initial value during this snap operation. A lever arm 47 projects from the rotary lever 43 and has a plurality of holding bores 48 arranged in a row and passing through it. In one of the holding holes 48, a tension spring 49 is suspended, which on the other hand is held on the switch housing 1 and acts as a torsion spring acting on the rotary lever 43 such a torque that its end 44 is present with a force on the switching plunger 45 which is less than that in the unswitched state , but larger than the one in the switched state of the microswitch 46 acting on the switching plunger 45 Is spring force. This dimensioning of the strength of the tension spring 49 forms, together with the microswitch 46 and the rotary lever 43, a bistable switching device, that is to say, in the absence of additional forces, the microswitch 46 maintains the unswitched switching position under the predominant spring load of its switching plunger 45, but in the switched state, under the predominant load by the tension spring 49 in the switched state. The microswitch 46 can be single or multi-pole, the cable connections are made through a housing part 50.

In the setting state according to the drawing, the spring plate 10 is in its uppermost screw position on the threaded spindle 13, the control spring 7 being set to the lowest pretension. The threaded sleeve 31 is also in its uppermost screw position in the switch housing 1, with its ring flange 33 abutting the shoulder surface 36. The nut 27 is also in its uppermost screw position on the threaded section 26, the distance between the individual stops 24 and 28 being only slightly larger than the strength of the lever end 42; the pressure switch is thus set to the lowest switching hysteresis. In the depressurized state shown, the control fields 7 hold the switching piston 3 in its lowest position, in which it is intercepted by contact with the switch housing 1. The rotary lever 43 is located by engaging its end 42 between the two individual stops 24 and 28 in its left rotational position, in which it holds the microswitch 46 under the force of the tension spring 49 when the switching plunger 45 is pressed in the switched position.

If pressure medium is supplied to the pressurizing chamber 4 through the line connection 5, the switching piston 3 begins to rise against the force of the control spring 7 when a certain pressure level is exceeded, taking the plunger 20 with it. During this stroke movement, the lower individual stop 28 immediately runs against the lever end 42 and takes it by turning the lever 43 to the right With. The switching plunger 45 is hereby released and expressed under its spring load from the microswitch 46 until the microswitch 36 snaps into its unswitched switching position, the suddenly increased spring load of the switching plunger 45 turning the rotary lever 43 into one of the rest positions of the switching plunger 45 corresponding to the rest position of the switching plunger 45 Position rotates. If the pressure in the pressurizing chamber 4 increases further, the individual stop 28 can come to rest against the rotary lever 43 and rotate it counterclockwise against the force of the tension spring 49 while lifting off the switching plunger 45; the uppermost stroke position of the switching piston 3 is limited by its contact with the lower end of the threaded spindle 13.

When the pressure in the pressurizing chamber 4 is subsequently reduced, the switching piston 3 lowers again under the force of the control spring 7, the rotary lever 43 rotating to the left under the force of the tension spring 49 until its lever end 44 abuts the switching plunger 45. When the switching piston 3 is lowered further, the rotary lever 43 remains in its position until the upper individual stop 24 comes to rest on the lever end 42 and, via this, rotates the rotary lever 43 further to the left. Here, the switching plunger 45 is pressed into the microswitch 46 until it snaps into its switched position, whereupon the tension spring 49 overcomes the pushing-out force of the switching plunger 45 and fully presses it in. Immediately afterwards, the switching piston 3 returns to its lowest position shown, determined by resting on the switch housing 1.

It is essential that when the pressure in the pressurizing chamber 4 rises, the switching of the microswitch 46 takes place by placing the lever end 42 against the lower individual stop 25, that is to say when the switching piston 3 is in a higher stroke position than when the pressure in the pressurizing chamber 4 drops, the microswitch 46 being switched by the system of the lever end 42 at the upper individual stop 24 and thus at a lower stroke position of the switching piston 3. The stroke position difference of the switching piston 3 corresponds to an application pressure difference for the switching piston 3, which represents a switching hysteresis.

After loosening the sealing wire 17, the spring plate 10 can be screwed downward on the threaded spindle 13, for example by means of a wrench, by rotating the hexagonal section 15, thereby increasing the pretension of the control spring 7 and thus increasing the switching pressure of the pressure switch. After setting the desired switching pressure, a new sealing wire 17 can be attached to secure. Since the distance between the individual stops 24 and 28 does not change when the switching pressure is set, the switching hysteresis remains constant in this setting process.

To change the switching hysteresis, the threaded sleeve 31 has to be unscrewed from the switch housing 1, for example by means of a wrench to be attached to the hexagonal section 34, after the sealing wire 41 has been loosened. When screwing the threaded sleeve 31, this takes the nut 27 with it via its inner profile surfaces 29, as a result of which it is screwed downward onto the threaded section 26 of the plunger 20 and the single stop 28 thus moves away from the single stop 24. The distance between the two individual stops 24 and 28 is thus increased; this increased distance corresponds to an increased stroke position difference of the switching piston 3 during the switching operations of the microswitch 46 and a correspondingly increased pressure difference and thus switching hysteresis. The threaded sleeve 31 can be unscrewed until its ring flange 33 strikes the lower shoulder surface 38; the greatest possible distance between the two individual stops 24 and 28 and thus the maximum switching hysteresis is then set.

The stroke limitation for the screwing of the threaded sleeve 31 by means of abutment of the ring flange 33 thereof on the switch surfaces 36 and 38 also limits the rotation and thus the screwing stroke of the nut 27 on the threaded section 26. Even when large rotational forces are applied to the threaded sleeve 31, jamming, for example jamming of the lever end 42, is thus between the individual stops 24 and 28 by setting a too small distance, safely excluded.

It may be expedient to first set the switching hysteresis and then the switching pressure when adjusting the pressure switch, since the distance of the lower individual stop 28 from the switching piston 3 changes when the switching hysteresis is set. On the other hand, however, it is also possible to first adjust the switch-on pressure for the microswitch 46 determined by the lever end 42 at the upper individual stop 24 and then the switching hysteresis with the switch-off pressure determined by the lever end 42 at the lower individual stop 28.

In a modification of the exemplary embodiment shown and described above, it is of course also possible to use a snap switch which is itself bistable from the outset instead of the monostable microswitch 46, which forms the bistable snap-action switching device together with the tension spring 49, the tension spring 49 can be omitted. Due to the reverse arrangement of the microswitch 46 offset downwards relative to the lever end 44 and the arrangement of the tension spring 49 offset upwards, the assignment of the switching pressurization of the switching piston 3 and the switching state of the microswitch 46 can be interchanged. Furthermore, it is possible to dimension the length of the threaded spindle 13 such that the switching piston 3 takes place at its lower end immediately after the microswitch 46 has been switched, before the lever end 44 is lifted off the switching plunger 45. Finally, the plunger 20 with the section 21, the single stop 24 and the threaded spindle 26 can be formed in one piece without a profile surface section 25, the single stop 24 is expediently formed by the lower end of the section 21 to be reinforced. On the other hand, the single stop 24 can also be formed by a cross pin to be inserted into the plunger 20.

The axially displaceable, non-rotatable guidance of the nut 27 on the threaded sleeve 31 can, of course, also be achieved by a different design of the inner profile surfaces 29, which are widely understood in their wording, than the above-described and shown prism-like guide device with a square, hexagonal or other polygonal surface cross section. In particular, this also includes a tongue and groove guide with a cross pin engaging in at least one axial groove of one part on the other part, a tongue and groove guide or the like.

A vent valve 51 of conventional design is provided for the atmospheric connection of the interior of the pressure switch which also surrounds the spring chamber 6.

Reference symbol list

• 1 switch housing
• 2 cylinder sections
• 3 switching pistons
• 4 pressurization room
• 5 line connection
• 6 spring chamber
• 7 control spring
• 8 spring plates
• 9 bullet
• 10 spring plates
• 11 nose
• 12 longitudinal slot
• 13 threaded spindle
• 14 ring flange
• 15 hexagon section
• 16 cross hole
• 17 sealing wire
• 18 bracket
• 19 seal
• 20 pestles
• 21 section
• 22 wall
• 23 section
• 24 single stops
• 25 profile surface section
• 26 threaded section
• 27 mother
• 28 single stop
• 29 inner profile surfaces
• 30 exemption
• 31 threaded sleeve
• 32 threaded section
• 33 ring flange
• 34 hexagon section
• 35 sealing ring
• 36 button
• 37 circlip
• 38 switch surface
• 39 cross hole
• 40 bracket
• 41 Sealing wire
• 42 end
• 24, 28, 42 stop device
• 43 rotary lever
• 44 end
• 45 switching plungers
• 46 microswitches
• 47 lever arm
• 48 holding hole
• 49 tension spring
• 50 housing part
• 51 vent valve

Claims (10)

1.Pressure switch with adjustable switching pressure and adjustable switching hysteresis, with a switching piston (3) acted upon by the switching pressure against the force of a control spring (7), with a single stop (24, 28) that can be moved by it and is effective in both directions of movement and has two axially offset movements Stop device (24, 28, 42) with an idle stroke, and with a bistable snap-action device that can be switched by the stop device, the force of the control spring (7) being determined by a first adjusting screw connection (10, 13) and the axial distance between the individual stops (24, 28 ) can be adjusted by a second adjusting screw connection (26, 27), characterized by the features, which are known per se, that
- The end of the control spring (7) facing away from the switching piston (3) is adjustably supported against the switch housing (1) via the first adjusting screw connection (10, 13),
- The switching piston (3) on its side facing away from the control spring (7) carries the two individual stops (24, 28) on a tappet (20),
- A rotatable part (27) of the second adjustment screw connection (26, 27) is axially displaceable and non-rotatably coupled to a threaded sleeve (31) which is adjustably screwed to the switch housing (1) and
- The manually rotatable threaded sleeve (31) can be screwed by means of two axial stops (36, 38) to the switch housing (1) by only a limited stroke. 2. Pressure switch according to claim 1, characterized in that the threaded sleeve (31) with a screwed to the switch housing (1) threaded portion (32), an optionally sealed on the switch housing (1) guided annular flange (33) and a protruding profile , optionally has a hexagonal section (34) and that the ring flange (33) is opposed on both sides by a shoulder surface (36, 38) of the switch housing (1), the axial distance between the shoulder surfaces (36, 38) being the thickness of the ring flange (33) around the maximum screw stroke of the threaded sleeve (31) exceeds. 3. Pressure switch according to claim 2, characterized in that the one single stop (24) is a fixed to the plunger (20), radial projection and the second single stop (28) from the end face of an adjustable with the plunger (20) screwed nut (27) and that the nut (27) engaging in an axial recess (30) of the threaded sleeve (31) is guided in the recess (30) in a non-rotatable and longitudinally displaceable manner, for example by means of profile surfaces (29). 4. Pressure switch according to claim 3, characterized in that the plunger (20) ends with a threaded portion (26) onto which the nut (27) is screwed. 5. Pressure switch according to claim 4, characterized in that the plunger (20) between the switching piston (3) and the single stop forming the radial projection (24) has a cylindrical portion (21) which is sealed axially displaceably in a loading space (4) for the switching piston (3) delimiting wall (22) of the switch housing (1). 6. Pressure switch according to claim 3, characterized in that the single stop (24) forming radial projection is formed by a plunger through the plunger (20), a ring shoulder located on the plunger or the like. 7. Pressure switch according to claim 1, characterized in that the control spring (7) is supported against a non-rotatably axially displaceable on the switch housing (1) guided spring plate (10) which is adjustably screwed with a threaded spindle (13) passing through it, and that the threaded spindle (13) is rotatable and at least axially immovably supported against the switch housing (1) in the effective direction of the control spring, the wall of which penetrates and ends outdoors with a profile, optionally hexagonal section (15). 8. Pressure switch according to claims 2 and 7, characterized in that the profile, optionally hexagonal sections (34, 15) of the threaded sleeve (31) and the threaded spindle (13) protrude at least approximately coaxially on opposite sides of the switch housing (1) from this and have transverse bores (39, 16) through which, on the other hand, lead wires (41, 17) which can be fixed on the switch housing (1) can be guided. 9. Pressure switch according to one or more of the preceding claims, characterized in that between the individual stops (24, 28) the end (42) of a rotary lever (43) engages, on which the switching plunger (45) of a monostable microswitch (46) rests, and that the rotary lever (43) is loaded in the switching direction of the microswitch (46) by a torsion spring, the strength of which is less than the force required to switch the microswitch (46) but greater than that on the switching plunger (45) when the microswitch (46) is switched. effective restoring force. 10. Pressure switch according to claim 9, characterized in that the rotary lever (43) has a lever arm (47) on which the torsion spring designed as a tension spring (49), optionally by hanging in one of several arranged in a row, the lever arm ( 47) penetrating holding holes (48) adjustable, attacks.

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