Elevator

Abstract

To keep an open state of a landing door.SOLUTION: An elevator 1 includes a moving member 5 provided on a landing door 41 and configured to take different postures in a storage state and an operating state with respect to the landing door 41. The moving member 5 has a lock portion configured to be locked to a door peripheral component positioned around the landing door 41 in a landing. In the storage state, the moving member 5 is disposed in a portion overlapping the landing door 41 in a front view and a rear view. In the operating state, the lock portion moves so as to protrude from a portion overlapping the landing door 41 in a front view and a rear view; and in this state, movement of the landing door 41 from an open state to a closed state is blocked by engagement with the door peripheral component.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an elevator capable of keeping a landing door open. [Background technology]

[0002] When performing maintenance on an elevator, the landing door may be held in an open state. For example, the door is opened to allow workers to enter and exit the landing and the elevator shaft, and to carry goods from the landing into the elevator shaft. The landing door is opened only when the car stops at the landing, and a door closing force is applied by providing a spring or the like so that the door is closed in other cases. For this reason, in order to hold the door open, workers carry a fixing device such as a rubber piece that can be fitted into the sill groove of the door (for example, the "door closing prevention device" described in Patent Document 1). By fitting this fixing device into the sill groove, the landing door, which is provided to move along the sill groove, is prevented from moving from the door open state to the door closed state due to the door closing force, and the door open state can be maintained.

[0003] However, the conventional method described above has the following problems. For example, if the fixing device is forgotten to be carried, a substitute device must be found at the work site, which reduces the efficiency of maintenance and other operations. Also, when attaching or detaching the fixing device to the sill groove, the fixing device may be accidentally dropped into the hoistway and lost. Thus, the conventional method has some inconveniences and there is room for improvement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-22748 A Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an elevator capable of keeping the landing doors open, which overcomes the inconveniences associated with conventional fixing devices. [Means for solving the problem]

[0006] The present invention provides an elevator comprising: a movable member that is provided on a landing door and has different postures with respect to the landing door in a stored state and an operating state, the movable member having an engagement portion that engages with a door-periphery component that is located around the landing door at the landing, the movable member being disposed in a portion that overlaps with the landing door in a front view and a rear view in the stored state, and the movable member being moved so that the engagement portion protrudes from the portion that overlaps with the landing door in a front view and a rear view in the operating state, and in this state, the movable member engages with the door-periphery component to prevent movement of the landing door from a door-open state to a door-closed state.

[0007] In this configuration, for example, during elevator maintenance, the landing door can be easily kept open by moving the locking portion of the moving member so as to protrude.

[0008] Further, the engagement of the locking portion can be achieved by generating a frictional force by contacting with the door peripheral component, thereby preventing the movement of the landing door.

[0009] In this configuration, the movement of the landing door is prevented by utilizing frictional force, so that the moving member can have a simple configuration.

[0010] Further, the engagement portion may be configured to abut against the door-periphery component in a direction along a moving direction of the landing door, thereby achieving the engagement and preventing the movement of the landing door.

[0011] In this configuration, the movement of the landing door is prevented by the abutment, so that the moving member can have a simple configuration.

[0012] The moving member may have a biasing portion that generates a biasing force, and the locking portion may receive the biasing force from the biasing portion in the acting state.

[0013] In this configuration, the engaging portion in the actuated state can be stabilized by the biasing portion.

[0014] The moving member may be provided on a side of the landing door closer to an opening formed when the door is opened.

[0015] In this configuration, the moving member is located in an easily reachable position, making it easy for an operator to operate the moving member.

[0016] The movable member may be configured to move from the stored state to the operating state by a single action.

[0017] This configuration is easy to use since the moving members are easy to operate. Effect of the Invention

[0018] In the present invention, the movable member provided on the landing door makes it easy to keep the landing door open, and therefore it is possible to provide an elevator capable of keeping the landing door open, which overcomes the inconveniences of the conventional fixing device. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing an elevator according to each embodiment of the present invention. [Diagram 2] FIG. 2(A) is a perspective view showing the right side in a simplified manner illustrating the configuration of a landing door in an elevator according to a first embodiment (basic example) of the present invention, and FIG. 2(B) is a perspective view showing the bottom in a simplified manner illustrating the configuration of a landing door in an elevator according to the first embodiment (variant example). [Diagram 3] FIG. 3 is a diagram showing a schematic configuration of a main part of an elevator hall door according to a second embodiment of the present invention. [Figure 4]FIG. 4 is a diagram showing a schematic configuration of a main part of an elevator hall door according to the third embodiment of the present invention. [Diagram 5] FIG. 5 shows a schematic configuration of a main part of a landing door in an elevator according to a fourth embodiment of the present invention, in which (A) is a vertical cross-sectional view showing the stored state, (B) is a plan view showing the stored state as viewed downward from inside the landing door, and (C) is a vertical cross-sectional view showing the operating state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Four embodiments of the present invention will now be described with reference to FIGS.

[0021] The configuration of the elevator 1 itself according to each embodiment is the same as that of a known elevator, and as shown in the schematic diagram of Fig. 1, includes a hoistway 2 extending vertically across multiple floors in a building, and a car 3 ascending and descending in the hoistway 2. The car 3 ascends and descends in the hoistway 2 and can stop at landings 4 provided on each floor of the building.

[0022] The car 3 is equipped with car doors 31 that communicate between the inside and outside of the car 3 by opening and closing. The car doors 31 in each embodiment are, for example, double-door doors with a pair (two) of opening and closing units (one door, or a unit composed of multiple doors that move in the same direction when opening and closing) provided symmetrically.

[0023] The landing 4 is provided with a landing door 41 that is opened and closed in the same unit as the car door 31. The landing door 41 is always kept in a door-closed state by a door-closing force applied by a spring or the like (not shown) provided on a door hanger or the like that supports the landing door 41, and when the car 3 stops at the landing 4, the landing door 41 is engaged with the car door 31 and opens and closes in conjunction with the car door 31 that is driven by the landing door 41 itself.

[0024] [First embodiment] First, the first embodiment will be described. The landing door 41 (only one of a pair of doors is shown) of the first embodiment is provided with a moving member 5. This moving member 5 is configured to assume different postures with respect to the landing door 41 in a stored state and an operating state. Fig. 2(A) shows the operating state.

[0025] The moving member 5 has a main body 51 and a locking portion 52. The main body 51 is provided so as to be able to appear and disappear from a door contact surface 411 (a surface on the side close to an opening formed so as to communicate with the inside of the car when the door is opened) of the landing door 41. The main body 51 in the first embodiment is rod-shaped. However, the present invention is not limited to this, and may be in another shape such as a plate-shaped shape. A base end of the rod-shaped main body 51 is supported by the landing door 41 in a rotatable state. A locking portion 52 is provided at a tip end of the rod-shaped main body 51. The locking portion 52 is a portion that locks with a door surrounding component positioned around the landing door 41 at the landing 4. The locking portion 52, together with the main body 51, is also able to appear and disappear from the door contact surface 411 of the landing door 41. In the first embodiment, the door surrounding component is the landing side sill (threshold) 42 in which a sill groove 421 that slidably supports the landing door 41 when it is opened and closed is formed (see FIG. 3). The locking portion 52 is formed from a material that generates elastic force when compressed, such as rubber, and is provided so as to cover the tip of the main body portion 51. The locking portion 52 is attached to the main body portion 51 by, for example, fitting. The locking portion 52 in the first embodiment is substantially spherical, but the shape is not particularly limited.

[0026] In the stored state, the moving member 5 is disposed at a portion overlapping the landing door 41 (the surface of the landing door 41 on the elevator shaft 2 side) in a front view (when facing the landing door 41 from the landing 4 side) and a rear view (when facing the landing door 41 from the elevator shaft 2 side). In the first embodiment, the moving member 5 is stored inside the landing door 41 and cannot be seen from the outside of the landing door 41. On the other hand, in the operating state, as shown in FIG. 2(A), the locking portion 52 moves so as to protrude from the portion overlapping the landing door 41 in a front view and a rear view. In this way, the moving member 5 can be moved between the stored state and the operating state and can be taken in and out through an opening 412 provided in a door stop surface 411 of the landing door 41. A cover (not shown) can also be attached to the opening 412 when the moving member 5 is stored. That is, the moving member 5 is disposed on the side close to the opening formed in the landing door 41 when the door is opened. In this arrangement, the moving member 5 is easy to operate and is therefore easy to use. In the operating state, the rod-shaped main body 51 extends in the axial direction so as to obliquely connect the door contact surface 411 (vertical surface) of the landing door 41 and the upper surface (horizontal surface) of the landing side sill 42. In the operating state, the locking portion 52 abuts against the upper surface of the landing side sill 42, or a part of the locking portion 52 enters the sill groove 421 and abuts against the inner surface of the sill groove 421. In the case of a configuration in which a part of the locking portion 52 enters the sill groove 421 and abuts against the inner surface of the sill groove 421, the thickness dimension of the locking portion 52 is formed larger than the width dimension of the sill groove 421 to an extent that a frictional force described below can be generated by compression. This abutment generates a frictional force between the locking portion 52 and the landing side sill 42, so that the two are engaged with each other. In this state where frictional force is generated, by interposing the movable member 5 between the landing door 41 and the landing side sill 42, even if a door closing force is applied to the landing door 41, the landing door 41 can be prevented from moving from the door open state to the door closed state by engaging with the landing side sill 42, which is a door peripheral component. Since the engagement is by frictional force, it is possible to stop the landing door 41 at any opening degree.

[0027] Here, since the moving member 5 in the first embodiment (basic example) shown in FIG. 2(A) is provided so as to protrude from and retract from the door stop surface 411 of the landing door 41, (the part in which the moving member 5 is stored) is present in a position visible to passengers of the elevator 1 through the opening 412. For this reason, there is a possibility that the moving member 5 may be tampered with by passengers or the like. In order to deal with this, as a modified example of the first embodiment, as shown in FIG. 2(B), the moving member 5 may be configured to protrude from and retract from the lower surface of the landing door 41. In this case, a lower opening 415 is provided on the lower surface of the landing door 41, and the moving member 5 can be inserted and removed through the lower opening 415. In this modified example, since the lower opening 415 is located in a position invisible to passengers, the moving member 5 can be completely hidden on the elevator shaft 2 side of the landing door 41 in a stored state, and therefore the possibility of tampering (such as putting the moving member 5 into an operating state without permission) can be eliminated.

[0028] [Second embodiment] Next, the second embodiment will be described. The differences from the first embodiment will be mainly described, and the configuration, function, and action that are not particularly described are the same as those of the first embodiment (the same applies to the third and fourth embodiments). The landing door 41 of the second embodiment is configured such that at least the portion where the moving member 5 is provided is not provided with a plate on the elevator shaft 2 side (FIG. 3 shows a configuration in which no plate is provided over the entire surface). The moving member 5 of the second embodiment has a pair of block-shaped shaft support parts 53 fixed to the lower part of the landing door 41, and a shaft part 54 supported away from the lower part of the landing door 41 by the pair of shaft support parts 53, 53. The shaft center of the shaft part 54 is in a horizontal direction parallel to the lower part of the landing door 41, and is provided along the opening and closing direction of the landing door 41. The shaft part 54 penetrates the locking part 55, which is a member having a U-shaped vertical cross section. The locking part 55 is rotatably supported by the shaft part 54, as shown by the arrow in FIG. 3. The reason for the "C" shape is to prevent the locking portion 55 in the activated state from interfering with the lower portion of the landing door 41 and the landing side sill 42. However, depending on the position where the shaft portion 54 is provided, the locking portion 55 may be a member having a vertical cross-sectional shape of another shape, such as an "L" shape or a "C" shape. The locking portion 55 can be formed from a hard material, such as a steel plate or a hard resin.

[0029] In the stored state, the locking portion 55 is located above the lower part of the landing door 41, as shown by the two-dot chain line in FIG. 3. On the other hand, in the operating state, a part of the locking portion 55 is located below the lower part of the landing door 41, as shown by the solid line in FIG. 3. In order to achieve such an operating state, a space that allows the locking portion 55 to rotate is provided on the side and under the landing side sill 42. This space is continuous with the space of the hoistway 2, for example. In addition, as shown in FIG. 3, a toe guard 43 is provided on the side of the landing side sill 42 on the hoistway 2 side. The toe guard 43 is a plate that is provided continuously below the landing side sill 42 to prevent passengers' feet from getting caught in a gap that appears in the lower part of the landing side sill 42 when the door opens while the car 3 is stopped at a position, for example, several tens of mm lower than the landing 4. The toe guard 43 is formed shorter than the landing side sill 42 based on the sill length, and is provided at a position where an end overlaps with the opening side end of the landing door 41 in the open state in the moving direction of the landing door 41. The lower part of the locking portion 55 in the operating state abuts against the end of the toe guard 43 in the door open state. Therefore, the locking portion 55 abuts against the toe guard 43, which is a door peripheral component, at the end surface 551 in the direction along the moving direction of the landing door 41, thereby engaging with each other and preventing the movement of the landing door 41. In other words, the toe guard 43 is positioned so as to overlap with the moving trajectory of the locking portion 55 when it is assumed that the locking portion 55 moves with the movement of the landing door 41, so that the locking portion 55 and the toe guard 43 abut against each other, and the movement of the landing door 41 is prevented via the locking portion 55. In this configuration, the principle of preventing the door movement is different from that of the first embodiment in that frictional force is not used. Also, the position where the landing door 41 is stopped is determined by the position of contact with the toe guard 43. In this configuration, the movement of the landing door 41 is prevented by the contact, so the moving member 5 can be configured simply. In the case of the toe guard 43, the tip end of the U-shaped portion in vertical cross section of the locking portion 55 (a plate-shaped portion that is approximately horizontal in the operating state) and the end face of the toe guard 43 (a door peripheral component) extending in the vertical direction are in contact with each other in a state where they intersect (in the second embodiment, they are approximately perpendicular). For this reason, even if the locking portion 55 is slightly misaligned in the rotation direction, the abutting state can be achieved.The abutment object of the locking portion 55 may be, for example, a Fescher plate in addition to the toe guard 43. The Fescher plate is a plate provided below the landing side sill 42 to prevent passengers from falling into the space of the hoistway 2 when the car 3 stops at a large deviation from the landing 4 compared to the case of the toe guard 43 and the passenger pries open the door to escape. The Fescher plate can be provided below the toe guard 43. Also, only one of the toe guard 43 and the Fescher plate can be provided below the landing side sill 42. In addition to these, a dead-end groove can be formed as the abutment object of the locking portion 55 in the part of the landing side sill 42 facing the hoistway 2, and the locking portion 55 can be configured to fit into this groove.

[0030] As described above, the movable member 5 of the first embodiment shown in Fig. 2(A) is provided so as to protrude from and retract from the door stop surface 411 of the landing door 41, and therefore may be tampered with by passengers, etc. In contrast, the movable member 5 of the second embodiment can be completely hidden on the elevator shaft 2 side of the landing door 41 in the stored state, and therefore the possibility of tampering can be eliminated.

[0031] [Third embodiment] Next, the third embodiment will be described. The third embodiment is similar in basic configuration to the second embodiment. The landing door 41 of the third embodiment is also configured such that at least the portion where the moving member 5 is provided, no plate is provided on the elevator shaft 2 side (FIG. 4 shows a configuration in which no plate is provided over the entire surface). The moving member 5 of the third embodiment has a shaft portion 56 provided at a lower corner of the landing door 41, and obliquely oriented so as to span the lower portion and side portion of the landing door 41. The shaft portion 56 penetrates a rotating portion 57 that is a member having a U-shaped vertical cross section, and the rotating portion 57 is supported by the shaft portion 56 so as to be rotatable. The reason for the U-shaped shape is to prevent the rotating portion 57 in the operating state from interfering with the side portion of the landing door 41. However, depending on the position where the shaft portion 56 is provided, the rotating portion 57 may be a member having another shape such as an L-shaped or C-shaped vertical cross section. The rotating part 57 can be formed from a hard material such as a steel plate or a hard resin. A locking part 58 is fixed to a radially outer position of the rotating part 57 based on the rotation reference. The locking part 58 is formed from a material that generates elastic force when compressed, such as rubber. The locking part 58 is attached to the rotating part 57 by, for example, gluing or fitting. The locking part 58 is triangular (specifically, a right-angled triangle) in front view and rear view with respect to the landing door 41 (the surface on the elevator shaft 2 side). The thickness dimension of the locking part 58 is formed to be larger than the width dimension of the sill groove 421 to an extent that a frictional force described later can be generated by compression.

[0032] In the stored state, the locking portion 58 is located above the lower part of the landing door 41, as shown by the two-dot chain line in FIG. 4. On the other hand, in the operating state, a part of the locking portion 58 is located below the lower part of the landing door 41, as shown by the solid line in FIG. 4. In order to achieve such an operating state, a space that allows the locking portion 58 to rotate is provided on the side and below the landing side sill 42. This space is continuous with the space of the elevator shaft 2, for example. In the operating state, a part of one side of the triangle enters the sill groove 421, and the part 581 of the locking portion 58 abuts against the inner surface of the sill groove 421. This abutment can generate a frictional force between the locking portion 58 and the landing side sill 42, and can prevent the landing door 41 from moving from the door open state to the door closed state with respect to the landing side sill 42, which is a door peripheral component.

[0033] [Fourth embodiment] Next, the fourth embodiment will be described. The fourth embodiment differs from the first to third embodiments in that the moving member 5 does not rotate. The moving member 5 of the fourth embodiment has a biasing portion 59 and a locking portion 510 that generate a biasing force. For example, a leaf spring is used for the biasing portion 59, and a base end portion is fixed to a lower portion of the landing door 41. In the stored state, the biasing portion 59 is in a state in which it extends linearly in the longitudinal direction as shown in FIG. 5(A), and in the operating state, it is in a state in which it is curved in the longitudinal direction so as to have an upward mountain as shown in FIG. In this curved state, the biasing portion 59 generates a biasing force. The locking portion 510 is formed of a material that generates an elastic force by compression, such as rubber, and is provided so as to cover the tip end portion of the biasing portion 59. The locking portion 510 is attached to the biasing portion 59 by, for example, fitting. Therefore, the locking portion 510 receives a biasing force from the biasing portion 59 in the operating state. The urging force stabilizes the locking portion 510 in the actuated state. In particular, when the urging force generated by the urging portion 59 is large, the engagement of the locking portion 510 with the landing side sill 42, which is a door peripheral component, is strengthened. The locking portion 510 in the fourth embodiment is cubic in shape, but the shape is not particularly limited. The thickness dimension of the locking portion 510 (the dimension that coincides with the width direction of the sill groove 421 in the actuated state) is formed larger than the width dimension of the sill groove 421 to an extent that a frictional force described later can be generated by compression. The locking portion 510 is provided so as to be able to appear and disappear from the lower portion of the landing door 41. In response to this, a locking portion through hole 413, which is a substantially square hole penetrating in the vertical direction, is provided at the lower part of the landing door 41, and in the stored state, the locking portion 510 is in a state of not protruding from the lower end surface of the landing door 41 as shown in FIG. 5(A), and in the operating state, the locking portion 510 is in a state of protruding from the lower end surface of the landing door 41 through the locking portion through hole 413 as shown in FIG. 5(C). At this time, the locking portion 510 is fitted into the locking portion through hole 413, so that the position of the locking portion 510 is maintained. In addition, a rectangular biasing portion side through hole 414 is provided at the lower part of the landing door 41 so as to be aligned with the locking portion through hole 413. This biasing portion side through hole 414 is used, for example, when bending the biasing portion 59. Furthermore, a plate material cut out to form the biasing portion side through hole 414 can also be used as a constituent material of the biasing portion 59.The locking portion 510 in the stored state abuts against the upper surface of the lower part of the landing door 41 as shown in FIG. 5(A). Therefore, the stored state is maintained. A part 5101 of the locking portion 510 in the operating state enters the sill groove 421 and abuts against the inner surface of the sill groove 421. This abutment can generate a frictional force between the locking portion 510 and the landing side sill 42. In this state where a frictional force is generated, the moving member 5 is interposed between the landing door 41 and the landing side sill 42, so that even if a door closing force is applied to the landing door 41, the landing door 41 can be prevented from moving from the door open state to the door closed state with respect to the landing side sill 42, which is a door peripheral component.

[0034] [Effect] According to each embodiment configured as described above, for example, during maintenance of the elevator 1, the locking portions 52, 55, 58, 510 of the movable member 5 can be moved so as to protrude, thereby easily maintaining the landing door 41 in an open state against the door closing force.

[0035] Moreover, the moving member 5 in the first to third embodiments moves from the stored state to the operating state by a single action, that is, a rotational action. Similarly, the movement from the operating state to the stored state is also performed by a single action. Similarly, the moving member 5 in the fourth embodiment moves from the stored state to the operating state by a single action, that is, an action of bending the biasing portion 59. Each of the embodiments configured in this manner is advantageous in that the moving member 5 is easy to operate and is therefore easy to use.

[0036] As a result, unlike the conventional case where an operator had to carry a fixing tool, the worker does not forget to carry the fixing tool and is unable to keep the door open, and when attaching or detaching the fixing tool from the sill groove, the fixing tool does not drop into the hoistway and get lost. Therefore, the inconveniences of the conventional fixing tool can be improved.

[0037] The elevator 1 of the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, part of the configuration of one embodiment can be deleted.

[0038] For example, in order to prevent the moving member 5 from moving in the stored state, a stopper that can switch between an engaged state and a disengaged state with the main body portion 51 in the first embodiment, the locking portion 52 in the second embodiment, the rotating portion 57 in the third embodiment, and the biasing portion 59 in the fourth embodiment can be provided. By providing a stopper in this manner, it is possible to prevent the moving member 5 from moving in an unexpected manner to an actuated state, for example, when the landing door 41 is opened or closed.

[0039] Furthermore, the movable member 5 is not limited to a configuration in which it is directly operated by an operator, but may be configured to be indirectly operated via an operating member provided in advance. In this case, by providing the operating member in a position where it is easy for an operator to operate, the workability during maintenance, etc. can be improved.

[0040] In the fourth embodiment, the locking portion is provided directly on the urging portion 59. However, this is not limited thereto, and for example, a separately configured urging portion 59 may be connected to the main body portion 51 of the first embodiment, the locking portion 52 of the second embodiment, and the rotating portion 57 of the third embodiment to exert a urging force on each of the above portions. [Explanation of symbols]

[0041] 1... elevator, 2... hoistway, 3... car, 31... car door, 4... landing, 41... landing door, 42... landing side sill, 421... sill groove (landing side sill), 43... toe guard, 5... moving member, 51... main body (first embodiment), 52... locking portion (first embodiment), 53... shaft support portion (second embodiment), 54... shaft portion (second embodiment), 55... locking portion (second embodiment), 56... shaft portion (third embodiment), 57... rotating portion (third embodiment), 58... locking portion (fourth embodiment), 59... biasing portion (fourth embodiment), 510 locking portion (fourth embodiment)

Claims

1. A movable member is provided on the landing door and has a different posture between a stored state and an operating state with respect to the landing door, The moving member has a locking portion that locks onto a door peripheral component located around the landing door at the landing, The moving member is In the stored state, the elevator is disposed in a portion overlapping the landing door in a front view and a rear view, In the actuated state, the locking portion is moved so as to protrude from a portion overlapping with the landing door in a front view and a rear view, and in this state, the locking portion is engaged with the door peripheral component to prevent the landing door from moving from a door-open state to a door-closed state. Elevator.

2. The elevator according to claim 1 , wherein the engagement is achieved by generating a frictional force by abutment against the door surrounding component, thereby preventing the movement of the landing door.

3. 2. The elevator according to claim 1, wherein the engagement is achieved by the locking portion abutting against the door-periphery component in a direction along a moving direction of the landing door, thereby preventing the movement of the landing door.

4. The moving member has a biasing portion that generates a biasing force, The elevator according to claim 1 , wherein the locking portion receives the urging force from the urging portion in the active state.

5. The elevator according to claim 1 , wherein the movable member is provided on a side of the landing door closer to an opening formed when the landing door is opened.

6. The elevator according to claim 1 , wherein the moving member is moved from the stored state to the operating state by a single operation.

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