DE3603591C1 - Pivoting-drive and locking mechanism for closure flaps of ventilation appliances - Google Patents

Abstract

A pivoting-drive and locking mechanism for closure flaps 12 of ventilation appliances is designed so that it can be actuated by an actuating lever 16 at one end of the housing of said appliances, but permits locking of the closure flap in its closed position at least at both housing ends. For this purpose, the actuating lever 16, pivotably mounted about a spindle 22, 23 arranged offset relative to the pivot bearing of the closure plate both in the height and depth direction, is provided, on the one hand, with a lifting curve 27 which is curved in its pivoting plane, has a varying distance relative to the bearing spindle 22, 23 at least over part of its length, and engages on a projection 28 at the end of the closure flap 12. The actuating lever 16 also has, however, a further lifting cam 30 directed transversely to its pivoting plane, with which a push-rod 15 is in actuating engagement, which is adjustably guided on the closure flap 12 at a distance from and parallel to its pivot bearing 13 and has at least one locking piece which can be brought into retaining engagement with a locking engagement at the other end of the housing (Fig. 3). <IMAGE>

Description

The invention relates to a rotary drive and locking gear for flaps of ventilation devices behind one with air through openings, in particular with perforations provided with space laterally arranged end plate, for example a cuboid Housing to one of its longitudinal edges is pivotally mounted and with an actuating lever which is pivoted parallel to it and is actuated engages, with the adjusting lever relative to the pivot bearing the flap is offset in both the vertical and the vertical direction arranged axis is pivotally mounted and one in the pivot has plane curved first stroke curve, which at least over part of their length a varying distance relative to the bearing axis has and engages a projection at the end of the closure flap.

Such a swivel drive and locking gear is already known by DE-GM 84 08 205. It is structurally designed so that it is one End of the cuboid housing and only there between it Housing and the closure flap both for opening and closing as well as locking the same is effective.  

In the case of ventilation devices with a relatively short overall length the well-known swivel drive and locking gear functionally be lasts. With larger lengths of the ventilation devices, which is quite The effect of this swivel can be up to 3000 millimeters drive and locking gear, however, inadequate because the same moderate tight closure of the flap over the entire length of the housing cannot be guaranteed permanently.

The invention aims to clear out the known Schwenkan drive and locking gear peculiar shortcomings. Des half the invention has for its object a swivel drive and Lock gearbox of the generic type to specify that in the closed position of the closure flap at least at both ends thereof locking effect and thereby the tight closure of the ventilation device optimized in the area of the air outlet openings on the room side.

This goal is achieved according to the invention according to the labeling feature paint of claim 1, namely in that the adjusting lever another, has a second stroke curve directed transversely to its swivel plane, consisting of trough, stroke curve and side surface, with the one Push rod is in engagement, which is at the closure flap at a distance is parallel to the pivot bearing and adjustable in an undercut longitudinal groove and at least has a locking piece with a housing-side locking engagement or abutment and a suit bevel can be brought in and out of the holding connection.

The swivel drive and locking gear according to the invention particularly advantageous in that it can be easily applied to any possible Can match the overall length of the ventilation devices, and simple in that the push rod is cut to a length, which the distance between the control lever mounted on one end of the housing and adapted to the latch engagement provided at the other end of the housing is. The lock is at one end of the ventilation device the closing flap in the closed position over the one with the first  Stroke engaging projection of the same causes while on the push rods directly opposite the end of the ventilation device ends with the housing-side latch engagement in holding connection.

In a further embodiment of the swivel drive and Locking gear is proposed according to claim 2, that the one Stroke curve a curved slot or a curved groove in the sides Surface of the lever is in which the projection of the closure flap protrudes while the second stroke curve is in the same one Side surface trained trough is located. Over the first stroke curve of the Control lever is an inevitable pivoting movement of the closure flap produced between their closed position and the open position, while the second stroke curve at least move the push rod non-positively can.

According to claim 3 is proposed that the trough or the second stroke curve is offset in the radial and circumferential directions to the first stroke curve in the side surface of the control lever, so that the projection cooperating with the first stroke curve the closure flap and the sliding rod guided on this radially one have different distance from the pivot bearing of the flap can.

So that the swivel drive and locking gear in one and the same version for optional installation on the right or left end of the ventilation device is suitable, according to claim 4 the adjusting lever to cut at right angles to its pivot axis Plane formed symmetrically, that is, in both sides with provided two stroke curves. If the actuating lever according to claim 5 is mounted on the inside of an end plate of a housing, it can according to claim 5 on the sides facing away from the end plate Surface, second stroke curve with one end in the closure  flap-guided push rod are in contact contact, while at least the other end of this push rod on the opposite end plate the case a tightening slope as bolt engagement and abutment is arranged. Between the second stroke curve of the control lever and the tightening oblique of the bolt engagement or abutment is in this embodiment the push rod is only motionally locked between its locking position and its unlocked position, moving into the Ent locking position depending on the opening swivel movement the flap arrives by the bolt engagement or abutment assigned end slides off at the bevel.

According to claim 6, it has also proven useful if the bevel with the bolt engagement or abutment parallel to Level of the end plate, preferably stepless, adjustable or adjustable is provided because the closing pressure for the closure is thereby ensured at all times can be tailored to existing needs. To this Purpose is according to claim 7, the actuator for the bolt intervention or the abutment formed by a screw spindle, which is rotatable but axially immovable in the end plate, and on its exposed End is provided with a tool intervention. The actuation of the screw Spindle can be made using a screwdriver, for example will.

It also turned out to be useful if according to claim 8, the push rod made of a wear-resistant plastic profile, which is in an undercut longitudinal groove on the closure flap is included. In the simplest case, the plastic can profile have a flat rectangular cross-section and only with its act directly from the end facing away from the lever as a locking piece. However, it could also have an approximately T-shaped cross section, wherein the T-bar protrudes from the longitudinal groove and is the same over its entire length has moderately distributed gears with the associated counter gears can enter into and out of operative connection within the housing.  

The latch cooperating with the free end of the push rod handle or the abutment can be according to claim 9 in one insert Pieces are located in a cutout of the end plate, but form fixed, held.

If then according to claim 10, the insert to a paral to the end plate The central plane is essentially symmetrically shaped and according to claim 11 the cutout for receiving the adjusting lever with the cutout structurally matches for the insertion of the insert in the end plates, can also be used for optional legal and Left installation can be used.

The swivel drive and locking gear is finally also there according to claim 12 by from that the adjusting lever on one of the protruding from the end plate Actuating cams diametrically opposite a tooth segment carries with which a drive pinion of an actuator can be brought into engagement is while in the area between the tooth segment and the actuation a driver can sit on the control lever with which an elec trical switching and / or control element for the drive motor of a blower an intervention can be brought.

In this way, a swivel drive and locking gear according to the invention can be used in many different ways, ie it can be used practically in one and the same design for ventilation devices which have the most varied of equipment. The control lever can not only be operated manually or indirectly by interposing a linkage via its actuating cam, but it can also be moved by an electric actuator. The control lever itself can also be used to switch an electrical blower installed in the ventilation device on and off or to regulate its working speed.

Embodiments of the invention shown in the drawing and described. It shows

Fig. 1 in three-dimensional view from the front view of the overall configuration of a ventilation device for spaces,

Fig. 2 in an enlarged view a cross section along the line II-II through the Lüftungsvor direction of FIG. 1,

Fig. 3 also in an enlarged illustration a section along the line III-III direction by the Lüftungsvor of FIG. 1 in in-opening position of the closure flap Lüftungsvor direction,

Fig. 4 a of Fig. 3 corresponding section but in the closed position of the closure flap,

Fig. 5 is a section along the line VV in Fig. 4,

Fig. 6 is a section along the line VI-VI in Fig. 1 and

Fig. 7 shows a section along the line VII-VII in Figs. 1 and 2, in each case only in the region of the two end plates of the housing of the ventilation device when the closure flap is in the closed position.

Fig. 1 of the drawing shows a ventilation device 1 for rooms in an overall view, which is preferably suitable for installation in fixed frames or sashes of windows and doors, but which, if necessary, can also be used in slot-like wall openings or placed on a wall.

The ventilation device 1 has an elongated, rectangular housing 2 , which is composed of an outer or rear wall 3 , an inner or front wall 4 , a ceiling wall 5 , a bottom wall 6 and two end plates 7 a and 7 b . Of Fig. 2 can be seen here that the outer or rear wall 3, the inner or front wall 4, the ceiling wall 5 and bottom wall 6 may be composed of thin-walled extrusions, respectively, which are preferably made of light metal. The outer or rear wall 3 is provided with air through openings 8 , which can be provided at greater intervals over its entire length.

In the inner or front wall 4 , on the other hand, there are air passage openings 9 in the form of a grid perforation which extends uniformly over the entire length and consists of several, for example three, rows of holes lying one above the other.

The outer or rear wall 3 is locked at its longitudinal edges via plastic profile bars 10 and 11 with the longitudinal edges of the ceiling wall 5 and the bottom wall 6 facing it, the plastic profile bars 10 and 11 forming a cold bridge between the outer and rear wall 3 on the one hand and the top wall 5 and the bottom wall 6 on the other hand. Inside the housing 2 , namely on the back of its inner or front wall 4 , a closure flap 12 is pivotally suspended in a pivot bearing 13 , with the aid of which the air passage openings 9 of the inner or front wall 4 can be released or completed. In Fig. 2 the closure flap 12 is shown in its open pivot position.

At its pivot edge 13 opposite the longitudinal flap 12 is provided with a dovetail or C-shaped undercut longitudinal groove 14 , in which a push rod 15 can be accommodated longitudinally, which in the exemplary embodiment according to FIG. 2 has a flat, rectangular cross section having. However, if necessary, it can also have a T-shaped cross-section, in which case the T-bar 15 ³ protrudes from the opening gap of the undercut longitudinal groove 14 , as is indicated in FIG. 2 by dash-dotted lines.

The ventilation device 1 of FIG. 1 is assigned a swivel drive and locking gear, from which in the area of the end plate 7 b only the adjusting lever 16 can be seen.

As a comparison of FIGS. 3 and 4 with FIG. 2 clearly shows, the end plate 7 b has an outline shape which is exactly adapted to the cross section of the housing 2 of the ventilation device 1 . The end plate 7 b has a cup-like shape, that is, web-like walls 18 protrude along its boundary edges, which have at least one course that overlaps with the walls 3, 4, 5, 6 of the housing 2 . The different wall webs are therefore marked with the reference numerals 18 ³ , 18 ⁴ , 18 ⁵ and 18 ⁶ . In the area of the wall webs 18 ⁴ , the end plate 7 b is provided with a cutout 19 , in the area of which the actuating lever 16 of the swivel drive and locking gear protrudes at least with its actuating cam 20 from the housing 2 . The adjusting lever 16 has circuit in the on to its actuating cam has a plate 21 with a bearing eye 22 which is slipped onto a bearing pin or a bearing sleeve 23 from the side which projects b from the inner surface of the end plate 7 in the same direction as the wall webs 18 ³ to 18 ⁶ . By means of the bearing eye 22 , the adjusting plate 21 of the adjusting lever 16 can be pivoted on the bearing sleeve 23 in the cutout 19 between two end positions, one of which can be seen from FIG. 3 and the other from FIG. 4.

In the pivot position of FIG. 3 of the cutout 19 is the actuating cam 20 of the actuating lever 16 at the upper end in the end plate 7 b, while it is in the other pivoting position at the lower end of the cutout 19.

The adjusting plate 21 of the actuating lever 16 is designed so that in the pivot position according to FIG. 3 with an arcuate surface 24 from the section 19 protrudes approximately segment-like, while in the pivot position according to FIG. 4 with a flat surface 25 the Cutout 19 closes flush.

At least in each case b of the end plate 7 facing away side surface 26 21, the adjusting plate of the adjusting lever 16, a first lifting cam 27, which as a laterally open groove is formed, and at least over part of its length a varying distance relative to the bearing 22 and the bearing sleeve 23 of the actuating lever 16 . The effective length of the first stroke curve 27 is matched to the maximum pivoting angle of the actuating lever 16 , the end region thereof having the greatest distance from the bearing 22 or the bearing sleeve 23 running concentrically to this bearing 22, 23 over a certain arc angle. The subsequent length range of this first stroke curve 27 , however, approaches the bearing 22, 23 of the actuating lever 16 to a minimal distance on a circular arc, the radius of which corresponds to approximately a quarter of the radius of the concentric section.

With the first cam 27 designed as a cam groove in the adjusting plate 21 of the actuating lever 16 , a pin 28 or a similar projection is in engagement, which is attached to the adjuster lever 16 end of the closure flap 12 so that it is with it about the pivot bearing 13 can shift on an arc. In the apparent from Fig. 3 pivot position of the control lever 16 of the pin 28 of the United flap 12 is in the region of the lower end of the first stroke curve 27 , that is, it is at its smallest distance from the bearing 22, 23 of the control lever.

In the pivoted position of the actuating lever 16 of FIG. 4, however, the pin 28 has passed the flap 12 in the region of the upper end of the first lifting cam 27, which at the greatest distance from the bearing 22, 23 has for the adjustment lever.

It is readily apparent that by pivoting the adjusting lever 16 between its two end positions shown in FIGS . 3 and 4, the closure flap 12 can be moved relative to the inner or front wall 4 of the housing 2 of the ventilation device 1 about the pivot bearing 13 , whereby it comes from the open pivot position according to FIGS. 2 and 3 into the closed position according to FIG. 4 and vice versa. In the closed position according to Fig. 4, thereby locking the shutter 12 at its one end by the interaction of the pin 28 with the first lifting cam 27th

By designing the first stroke curve 27 as a cam groove or cam slot, the closure flap 12 is positively controlled by the actuating lever 16 in both possible directions of movement via the pin 28 .

At least in the side surface 26 b facing away from the end plate 7 b of the adjusting plate 21 , both in the radial direction and in the circumferential direction at an angle relative to the first lifting curve 27, a trough 29 is formed, which extends transversely to the pivoting plane of the adjusting lever 16 , lifting curve 30 runs out into the side surface 26 of the adjusting plate 21 . The ending in the side surface 26 end portion of the stroke curve 30 is in the vicinity of the actuating cam 20 for the actuating lever 16 , as can be seen clearly in FIGS . 3 and 4.

With the trough 29, the issuing therefrom lift curve 30 and the side surface 26 of the actuating plate 21 acts in accordance with FIGS. 5 and 7 of the drawing, the control lever 16 of the Schwenkantriebs- and locking gear facing towards end 15 ¹ of the push rod 15 together, the hinterschnit in the ten profiled longitudinal groove 14 of the closure flap 12 is guided to be longitudinally movable.

In the pivoted position of Figure 3 befindlichem actuating lever 16. Is received the end 15 ¹ of the recess 29 in the side surface 26 of the adjusting plate 21, that is, it projects far out from the plate of the end 7b facing the end of the closure flap 12 out. If the control lever 16 from the pivotal position shown in FIG. 3 in the direction of the pivot position of FIG. 4 moves, then the end of 15 ¹ is running the push rod 15 inner half of the trough 29 to the transversely inclined to the pivot plane lift curve 30 and is thereby gradually to the adjacent end of the closing flap 12 to be moved until it bears in the pivoted position according to FIG. 4 on the side surface 26 of the adjusting plate 21 , as can be seen particularly clearly from FIG. 5.

The locking piece 15 ^{2 of} the push rod 15 assigned to the other end of the closure flap 12 interacts in the area of the end plate 7 a of the housing 2 with a locking engagement or abutment 31 , the arrangement and design of which can be seen in FIGS . 6 and 7 of the drawing. Fig. 7 makes it clear that the bolt engagement or the abutment bearing 31 has an inclined against the plane of the end plate 7 a and also against the loading direction of the push rod 15 tightening bevel 32 . The tightening bevel 32 is placed so that when the locking piece 15 ² hits the connecting rod 15 leading the closing flap 12 in the direction of its closed position against the back of the inner or front wall 4 of the housing 2 and consequently the air passage openings 9 sealed in this.

So that the pressure effect of the closure flap 12 can be varied by the locking piece 15 ^{2 of} the push rod 15 , the locking engagement or the abutment 31 is provided parallel to the plane of the end plate 7 b , preferably continuously, adjustably or adjustably. For this purpose he sits in an insert 33 which closes the cut-out 19 in the wall web 18 ^{4 of} the end plate 7 a with support with a support plate 34 and thereby includes the bearing sleeve 23 on the inside of the end plate 7 a fixing by means of a loop 35 . The bolt engagement or the abutment 31 with the bevel 32 consists of a metal bracket, preferably made of spring steel, which is received with its one leg 31 ¹ and its web 31 ² in a guide 36 of the insert 33 , while its leg 31 ³ with the Web 31 ² outgoing suit inclined 32 protrudes sideways from the guide 36 , as can be seen in Fig. 7.

The web 31 ^{2 of} the bolt engagement or abutment 31 contains a threaded hole 37 which is penetrated by the shaft of a screw 38 which is only rotatable with its head 39 , but axially immovable in a holder 40 on the support plate 34 of the insert 33 . Before the bracket 40 is in the support plate 34, a hole 41 through which a screwdriver with the slot in the screw head 39 can be brought into a handle. By turning the screw, the locking engagement or the abutment 31 in the guide 36 of the insert 33 can be shifted so that the bevel 32 is also subject to a corresponding change in position in order to adjust the pressing action of the push rod 15 via its locking piece 15 ² .

The push rod 15 can preferably be made of wear-resistant plastic, the locking piece 15 ² having a certain elasticity of the leg 31 ³ with the bevel 32 on the locking engagement or abutment 31 underneath and thereby also exerting a resilient pressing action on the closure flap 12.

It is advantageous if, on the one hand, the actuating lever 16 is designed symmetrically transversely to its pivoting plane, that is to say it has first lifting curves 27 , troughs 29 and lifting curves 30 on both side surfaces 26 of its adjusting plate 21 , as shown in FIG. 5. On the other hand, the insert 33 also has a symmetrical design with respect to a plane that runs parallel to the end plates 7 a and 7 b . It is thus easily and easily given the opportunity to assign both the control lever 16 and the insert 33 either the end plate 7 a or the end plate 7 b . The swivel drive and locking gear for the closure flap can therefore be changed at any time, even later, in its installed position for the housing 2 of the ventilation device 1 .

FIGS. 3 and 4 of the drawing can still be seen that the adjusting plate 21 at a the actuating cam 20 approximately diametrically opposite point can be provided with a toothed segment 42 of the actuating lever 16 to which can bring an electric servo motor engages the pinion, if it is desired to actuate the swivel drive and locking mechanism by an electric servomotor, which is then housed within the housing 2 of the ventilation device 1 . In addition, however, the adjusting plate 21 of the adjusting lever 16 can also be equipped with a driver 43 , for example in the form of a radial slot, with which an electrical switching and / or locking element can be coupled if the ventilation device is equipped with an electrically driven fan.

Due to the swivel drive and locking gear, the Blower drive motor can be switched on and off, and it can be if necessary also regulate its speed in this way, the swivel angle of the control lever each be a measure of the working speed of the fan can.

If the push rod 15 has a T-shaped cross section, it can be provided from the undercut longitudinal groove 14 projecting T-web 15 ³ with a toothing ver running in its longitudinal direction. A longitudinal toothed rail 44 is then assigned to it on the inner or front wall 4, as shown in FIG . B. in an undercut groove of the same in the longitudinal direction. By interlocking the T-bar 15 ³ and the longitudinal toothed rail 44 , the closure flap 12 can then be locked and pressed over its entire length in the closed position.

Claims (12)

1. Swivel drive and locking gear for closure flaps of ventilation devices, which is arranged behind an opening with air passage openings, in particular with grille perforations, provided on the room side, for example a cuboid housing, is pivotally mounted about one of its longitudinal edges and has a control lever pivotally mounted parallel to it is in operating engagement, the adjusting lever is pivotally mounted about an axis which is offset relative to the pivot bearing of the closure flap both in the vertical and in the vertical direction and has a curved first stroke curve in the pivot plane, which has a varying distance at least over part of its length to the bearing axis and engages a projection at the end of the closure flap, characterized in that the adjusting lever ( 16 ) on a positioning plate ( 21 ) has a further, transversely to its pivoting plane directed second stroke curve consisting of Mul de ( 29 ), stroke curve ( 30 ) and side surface ( 26 ), with which a push rod ( 15 ) is in engagement, which is adjustable on the closure flap ( 12 ) at a distance parallel to its pivot bearing ( 13 ) in an undercut longitudinal groove ( 14 ) is guided and has at least one locking piece ( 15 ² ) which can be brought into and out of a holding connection with a locking engagement or abutment ( 31 ) on the housing side and a tightening slope ( 32 ). 2. Swivel drive and locking gear according to claim 1, characterized in that the first lifting curve ( 27 ) is a curved slot or a GE curved groove in the side surface ( 26 ) of the actuating lever ( 16, 21 ) into which the pin ( 28 ) of the closure flap ( 12 ) protrudes sideways, while the second stroke curve ( 29, 30, 26 ) is located in a recess ( 29 ) formed in the side surface ( 26 ) of the adjusting plate ( 21 ) of the adjusting lever ( 16 ). 3. swivel drive and locking gear according to one of claims 1 and 2, characterized in that the trough ( 29 ) or the second stroke curve ( 29, 30, 26 ) angularly offset both in the radial direction and in the circumferential direction to the first stroke curve ( 27 ) in the side surface ( 26 ) of the adjusting plate ( 21 ) of the adjusting lever ( 16 ) is ( Fig. 3 and 4). 4. Swivel drive and locking gear according to one of claims 1 to 3, characterized in that the adjusting lever ( 16 ) is symmetrical to a plane intersecting its swivel axis at right angles, that is, in both side surfaces ( 26 ) each with a first and a second stroke curve ( 27 and 29, 30, 26 ) is provided ( Fig. 5). 5. swivel drive and locking gear according to one of claims 1 to 4, characterized in that the adjusting lever ( 16, 21 ) on the inside of an end plate ( 7 a and 7 b) of a housing ( 2 ) is mounted ( 22, 23 ) and via the second stroke curve ( 29, 30, 26 ) located in its side surfaces ( 26 ) facing away from the end plate ( 7 a or 7 b) , with one end ( 15 ¹ ) of the undercut longitudinal groove ( 15 ) in the closure flap ( 12 ) 14 ) guided push rod ( 15 ) is in tact contact, while at least on the locking piece ( 15 ² ) of the push rod ( 15 ) on the opposite end plate ( 7 b and 7 a) of the housing ( 2 ) a tightening slope ( 32 ) the bolt engagement or Abutment ( 31 ) is assigned ( FIGS. 6 and 7). 6. swivel drive and locking gear according to one of claims 1 to 5, characterized in that the tightening slope ( 32 ) with the bolt engagement or abutment ( 31 ) parallel to the plane of the end plate ( 7 b or 7 a) preferably continuously, adjustable or . -Adjustable is provided ( Fig. 6 and 7). 7. swivel drive and locking gear according to one of claims 1 to 6, characterized in that the actuator or adjusting element, consisting of a threaded hole ( 37 ) and a screw ( 38 ) with head ( 39 ) for the locking engagement or the abutment ( 31 ) rotatable bar, but axially immovable in the end plate ( 7 b or 7 a) in a holder ( 40 ) and on the head ( 39 ) with a tool handle, z. B. a transverse slot is provided. 8. swivel drive and locking gear according to one of claims 1 to 7, characterized in that the push rod ( 15 ) consists of a wear-resistant plastic profile which is received in the undercut longitudinal groove ( 14 ) on the closure flap ( 12 ). 9. swivel drive and locking gear according to one of claims 1 to 8, characterized in that the bolt engagement or the abutment ( 31 ) is in an insert piece ( 33 ) which in a cutout ( 19 ) of the end plate ( 7 b or 7 a) is held releasably but positively by means of a support plate ( 34 ), a loop ( 35 ) and a guide ( 36 ). 10. swivel drive and locking gear according to one of claims 1 to 9, characterized in that the insert ( 33 ) to a to the end plate ( 7 b or 7 a) parallel central plane substantially symmetrical and suitable for optional right and left installation is. 11. Swivel drive and locking gear according to one of claims 1 to 10, characterized in that the cutout ( 19 ) for receiving the actuating lever ( 16 ) and the adjusting plate ( 21 ) in the end plates ( 7 a and 7 b) the cutout ( 19 ) for receiving the insert support ( 33 ). 12. Swivel drive and locking gear according to one of claims 1 to 11, characterized in that the adjusting lever ( 16 ) and the adjusting plate ( 21 ) on one of the end plate ( 7 a and 7 b) projecting actuating cam ( 20 ) approximately diametrically opposite a toothed segment ( 42 ) with which a drive pinion of an actuator can be brought into engagement, while in the area between the toothed segment ( 42 ) and the actuating cam ( 20 ) a driver ( 43 ) sits with which an electrical switching and / or locking member for the drive motor of a blower can be brought into engagement.