Attachment Attaching/Detaching Device

The present disclosure relates to an attachment attaching/detaching device that is interposed between an arm of a construction machine and an attachment.

There is a known attachment attaching/detaching device, which is interposed between an arm of a construction machine and an attachment, in a configuration that includes an arm connection part to which an arm and a rod or a link are connected and which is provided with a fixed hook that engages a first pin of an attachment, and a movable hook that moves toward and away from the fixed hook and engages a second pin of the attachment (JP 2021-161788 A). The attachment attaching/detaching device disclosed in Patent Literature 1 has a key block that can freely advance and retreat along an inner peripheral edge of the fixed hook, and even in a case where the movable hook becomes disengaged from the second pin of the attachment, the first pin of the attachment does not become disengaged from the fixed hook, and thus the safety at the time of detaching an attachment is increased.

An advantageous effect produced by a locking mechanism typified by a key block is the safety at the time of detaching an attachment associated with the attachment attaching/detaching device disclosed in JP 2021-161788 A. Many other traditional attachment attaching/detaching devices are also equipped with such kind of locking mechanism. In some cases, however, a locking mechanism may not be employed in a smaller attachment attaching/detaching device in which space for arranging the locking mechanism cannot be secured. In the case of an attachment device that does not have a locking mechanism, if the movable hook becomes disengaged from the second pin, the first pin may also become disengaged from the fixed hook depending on the tilted posture of the attachment (a posture determined by rotation around an arm connecting shaft), and in the worst case there is a risk that the attachment will fall off.

Currently, it is necessary to rely on visual observation by the operator to check the tilted posture of an attachment, which makes it difficult to ensure a safe tilted posture. Further, in some cases the movable hook is moved unconsciously in an attempt to detach the attachment, without checking the tilted posture of the attachment. Consequently, with respect to an attachment attaching/detaching device that does not have a locking mechanism, the safety at the time of detaching an attachment has not been sufficient. Therefore, with regard to attachment attaching/detaching devices that do not have a locking mechanism, studies have been conducted for realizing safety securing means in place of a locking mechanism so that, even if the movable hook becomes disengaged from the second pin, the attachment can be detached without the first pin becoming disengaged from the fixed hook.

A device that has been developed as a result of the aforementioned studies is an attachment attaching/detaching device including an arm connection part to which an arm and a rod or a link are connected, the arm connection part provided with a fixed hook that engages a first pin of an attachment, and a movable hook that moves toward and away from the fixed hook and engages a second pin of the attachment, wherein a tilt switch that switches between allowing a flow of current and cutting off a flow of current depending on a tilted posture is mounted to the arm connection part in a state in which the tilt switch is interposed along a power supply line or a signal line to electric driving means for causing the movable hook to advance or retreat.

In the attachment attaching/detaching device of the present disclosure, a tilt switch that switches between allowing a flow of current and cutting off a flow of current depending on a tilted posture is used so that the movable hook is not allowed to advance or retreat unless the attachment attaching/detaching device assumes a specific turned posture. The tilt switch takes a horizontal state as a reference state, and allows a flow of current when one end (for example, a cable lead-out end) descends relative to the horizontal state, and cuts off the flow of current when the one end rises relative to the horizontal state. The relation between the tilted posture of the tilt switch and allowing the flow of current and cutting off the flow of current may be the reverse of the aforementioned relation. Thus, the tilt switch can be mounted to the arm connection part in such a manner that one end of the tilt switch descends from a horizontal state in accordance with a tilted posture of the attachment attaching/detaching device, at which posture no problem occurs even if the movable hook advances or retreats. In this way, the flow of a current to a power supply line or a signal line of the electric driving means is cut off and the electric driving means is not activated unless the attachment attaching/detaching device assumes a specific tilted posture, and thus the movable hook can be prevented from advancing and retreating.

The electric driving means may be any driving means with which advancing and retreating of the movable hook is electrically controlled directly or indirectly. The power supply line supplies electric power for driving to the electric driving means. The signal line transmits control signals that activate or stop the electric driving means. The tilt switch is interposed along either one of the power supply line and the communication line so that advancing and retreating of the movable hook can be regulated. Here, in a case where the movable hook is caused to advance and retreat using a hydraulic cylinder, preferably the electric driving means is configured as a hydraulic cylinder to which an electromagnetic valve that switches a connection port when a current flows to the power supply line or the signal line is connected. An operation switch or an operation lever for the power supply line or the signal line is provided at the driver's seat, and the tilt switch is interposed along the power supply line or the signal line inside the attachment attaching/detaching device.

Preferably, the tilt switch is mounted to the arm connection part in a tilted posture such that the tilt switch allows the flow of current if the center of gravity of the attachment attached to the attachment attaching/detaching device is located on a side which is further away from the movable hook than a position directly below the center of the fixed hook. By this means, in a state in which the tilt switch allows the flow of current, which is equal to a state in which the movable hook can advance and retreat, a state can be entered in which a rotational force in a direction that brings the second pin closer to the movable hook that is centered on the first pin which is engaged with the fixed hook is imparted to the attachment, and the risk of the first pin disengaging from the fixed hook is approximately eliminated.

In the attachment attaching/detaching device of the present disclosure, a tilted posture of the tilt switch that is required when mounting the tilt switch to the arm connection part differs slightly depending on the type of attachment to be connected to the attachment attaching/detaching device. From this point on, preferably the tilted posture at which the tilt switch is mounted to the arm connection part is freely adjustable. Because the tilted posture of the tilt switch is freely adjustable, the tilted posture can be adjusted each time an attachment connected to the attachment attaching/detaching device changes, and a tilted posture that allows the movable hook to advance and retreat can be specified for each attachment. Examples of adjustment means for adjusting the tilted posture that may be mentioned include a configuration in which the tilt switch is mounted on a rotatable base provided on the connecting arm part, and a configuration in which a bolt that fixes the tilt switch to the connecting arm part is passed through a long hole.

The attachment attaching/detaching device of the present disclosure can prevent the movable hook from advancing and retreating unless the attachment attaching/detaching device assumes a specific tilted posture. This is an advantageous effect achieved by the tilt switch mounted to the arm connection part. By this means, the risk that, when the movable hook is detached from the second pin of the attachment, the attachment will rotate around the first pin and will fall off from the attachment attaching/detaching device can be reduced or eliminated. In this way, the safety is ensured when detaching an attachment in an attachment attaching/detaching device that does not have a locking mechanism.

In the attachment attaching/detaching device of the present disclosure, the tilt switch that switches between allowing the flow of current and cutting off the flow of current depending on a tilted posture is used so that the movable hook is not allowed to advance or retreat unless the attachment attaching/detaching device assumes a specific tilted posture. The tilt switch takes the horizontal state as a reference state, and allows (or cuts off) a flow of current when one end (for example, a cable lead-out end) thereof descends relative to the horizontal state, and cuts off (or allows) the flow of current when the one end rises relative to the horizontal state. Thus, the tilt switch can be mounted to the arm connection part in such a manner that one end of the tilt switch descends from a horizontal state in accordance with a tilted posture of the attachment attaching/detaching device, at which posture no problem occurs even if the movable hook advances or retreats. In this way, the movable hook can be prevented from advancing and retreating unless the attachment attaching/detaching device assumes a specific tilted posture.

If the electric driving means is configured as a hydraulic cylinder connected to an electromagnetic valve that switches a connection port when a current flows to the power supply line or the signal line, the present disclosure can be applied to a hydraulic system used in a construction machine as is by merely interposing the tilt switch along a power supply line or a signal line of the electromagnetic valve. This means that the present disclosure can be constructed without requiring a major modification to an existing attachment attaching/detaching device as long as there is sufficient installation space for mounting the tilt switch in an arm connection part. Hence, the present disclosure can be easily used in a small-sized attachment attaching/detaching device that does not have a locking mechanism.

When the tilt switch is mounted to the arm connection part in a tilted posture such that the tilt switch allows the flow of current if the center of gravity of the attachment attached to the attachment attaching/detaching device is located on a side which is further away from the movable hook than a position directly below the center of the fixed hook, in a state in which the tilt switch allows the flow of current, for example, a state can be entered in which the second pin is pressed against the pin receiver of the arm connection part that faces the movable hook and the first pin does not disengage from the fixed hook, and therefore the attachment can be prevented from falling out due to inadvertent rotation of the attachment. Such a tilted posture of the tilt switch differs for each attachment to be attached to the attachment attaching/detaching device, and is determined individually.

Further, when the tilted posture at which the tilt switch is mounted to the arm connection part is freely adjustable, the tilted posture of the attachment attaching/detaching device at which the tilt switch allows the flow of current can be freely determined. The tilt switch whose tilted posture is freely adjustable is suitable for a case where the tilted posture of the tilt switch that can prevent an attachment from falling out due to inadvertent rotation of the attachment is adjusted according to the combination of the attachment attaching/detaching device and the attachment. By this means, even if the attachment attached to the attachment attaching/detaching device is changed, the present disclosure can be utilized by merely adjusting the tilted posture of the tilt switch.

Hereunder, one form for carrying out the present disclosure is described while referring to the accompanying drawings. An attachment attaching/detaching deviceof the present disclosure that does not have a locking mechanism is suitably used in a small-sized construction machine, as illustrated in. The attachment attaching/detaching deviceof the present example connects an armof the construction machineand a linkextending from a swing leverto which a rod for an attachmentof a hydraulic cylinder for an attachmentis connected, to an arm connection part, and causes a first pinto engage with a fixed hookand causes a second pinto engage with a movable hookto thereby attach an attachment (in the present example, a bucket)to the arm connection part. An operation switch(see) for performing operations to advance and retract the movable hookis provided in a driver's seat.

As illustrated in, the attachment attaching/detaching deviceof the present example is constituted by a hydraulic system(indicated by a thick line) that causes the movable hookto advance and retreat and an electrical system(indicated by a thin line) which are the same as the traditional hydraulic system and electrical system, and a tilt switchthat is additionally provided in the electrical system. The tilt switchdoes not require any external operating means, and only needs to be interposed along a power supply line or a signal line of the electrical system. Furthermore, the tilt switchis small and does not require a large installation space. Thus, the present disclosure can be utilized by adding the tilt switchto an attachment attaching/detaching devicewhich is already manufactured, and provides the advantage that safety at the time of detaching the attachmentcan be added to an attachment attaching/detaching devicewhich is already manufactured that does not have a locking mechanism.

The arm connection parthas a structure in which two side platesmade of metal which are each substantially a parallelogram in side view are held parallel to each other, and all or one part of the hydraulic systemand the electrical systemis arranged between the side plates. The tilt switchof the present example has a cylindrical shape extending from one end to which a shared power supply lineis connected, and is fixed to the inner side of one of the side platesby a first fixing boltwhich is closer to one end side, and a second fixing boltwhich is closer to the other end side. The second fixing boltfixes the tilt switchby passing through an arcuate long holeprovided in the side plate. The arcuate long holeis a curved long hole which is centered on the first fixing bolt. Thus, the tilted posture of the tilt switchcan be adjusted by changing the fixing position of the second fixing boltwith respect to the arcuate long hole.

In the arm connection part, an arm connection shafton one end side (right side in) of a concave upper edge of the side plateand a link connection shafton the other end side (left side in) are provided spanning between the left and right side plates, with the armbeing rotatably connected to the arm connection shaft, and the linkbeing rotatably connected to the link connection shaft. Further, in the arm connection part, a hook-shaped fixed hookthat opens outward is provided on one end side of a linear lower edge of each side plate. Since the fixed hookis provided in each of the side plates, there is a pair of left and right fixed hooks, and each of the fixed hooksis engaged with the first pinof the attachment.

In the arm connection part, a pin receiverhaving the shape of a substantially ¼ arc that opens downward is formed on the other end side of the linear lower edge of each side plate. The movable hookis a hook-shaped portion in side view that is in internal contact with the side platesand protrudes in the forward direction (the left direction in) from a metal blockthat moves forward and backward. The pin receiverand the movable hookthat has advanced to a position directly below the pin receiverare in a positional relationship in which they face each other in the vertical direction, and in a state in which the pin receiverrestrains the left and right sides of the second pinof the attachmentfrom above, the movable hooksupports the middle part between the left and right sides of the second pinfrom below to thereby sandwich the second pin. When the movable hookretreats, the second pinis released at the lower part of the pin receiver, and the second pinseparates from the pin receiver.

The metal blockincorporates therein a tube of a hydraulic cylinder for a hook, and connects a rod for a hookto a position fixing blockthat is fixed to the side plate. By this means, when the rod for a hookis expanded or contracted, the metal blockapproaches or moves away from the position fixing block, and thus the movable hookcan advance and retreat. The hydraulic cylinder for a hookmay connect the tube to the position fixing block, and connect the rod for a hookthat expands and contracts to the metal block.

The hydraulic systemof the present example has a configuration in which a tank-side first hydraulic lineand a tank-side second hydraulic linethat are connected to an oil tank, and a cylinder-side first hydraulic lineand a cylinder-side second hydraulic linethat are connected to the hydraulic cylinder for a hookare connected through an electromagnetic valvethat is a three-position switching valve. The tank-side first hydraulic lineis provided with a hydraulic pump. In the present example, electric driving means for the movable hookis constituted by the electromagnetic valveand the hydraulic cylinder for a hook.

The cylinder-side first hydraulic lineis provided with a first check valvethat is connected to a base end side (left side in) of the tube of the hydraulic cylinder for a hook, and at which a first pilot lineis connected to the cylinder-side second hydraulic line. The cylinder-side second hydraulic lineis provided with a second check valvethat is connected to a rod side (right side in) of the tube of the hydraulic cylinder for a hook, and at which a second pilot lineis connected to the cylinder-side first hydraulic line.

As long as oil does not flow into either of the cylinder-side first hydraulic lineand the cylinder-side second hydraulic line, the first check valveand the second check valveprevent the movement of oil that remains in the tube of the hydraulic cylinder for a hook, and thereby ensure that the movable hookdoes not move inadvertently. In the attachment attaching/detaching deviceof the present example, unless the tilt switchhas assumed a specific tilted posture, the supply of electric power to the tilt switchis cut off and the electromagnetic valveis not actuated. This creates a state in which oil does not flow to either of the cylinder-side first hydraulic lineand the cylinder-side second hydraulic linewhen the attachment attaching/detaching devicehas assumed a posture other than a specific tilted posture, and thus safety such that the movable hookcannot be moved is achieved by utilizing the action of the first check valveand the second check valve.

In the electromagnetic valve, when electric power is supplied from a first power supply lineto a solenoid for a first sectionby operation of the operation switch, the electromagnetic valveis pushed by the solenoid for a first sectionand switches a connection relationship between the hydraulic lines from a central sectionto a first section. Further, when the operation switchis switched to a neutral state from the power supply state and the power supply from the first power supply lineis stopped, the electromagnetic valveis pulled back by the action of urging means (for example, a coil spring), and the connection relationship between the hydraulic lines returns to the central sectionfrom the first section.

In the electromagnetic valve, when electric power is supplied from a second power supply lineto a second section solenoidby operation of the operation switch, the electromagnetic valveis pushed by the second section solenoidand switches the connection relationship between the hydraulic lines from the central sectionto a second section. Further, when the operation switchis switched to a neutral state from the power supply state and the power supply from the second power supply lineis stopped, the electromagnetic valveis pulled back by the action of urging means (for example, a coil spring), and the connection relationship between the hydraulic lines returns to the central sectionfrom the second section. The central sectioncuts off the connection between the tank-side first hydraulic lineand the cylinder-side first hydraulic line, and connects the cylinder-side first hydraulic lineand the cylinder-side second hydraulic line.

The first sectionconnects the tank-side first hydraulic lineand the cylinder-side first hydraulic lineand connects the tank-side second hydraulic lineand the cylinder-side second hydraulic line, to thereby send oil from the tank-side first hydraulic lineto the base end side of the tube of the hydraulic cylinder for a hookvia the cylinder-side first hydraulic line, and return oil from the rod side of the tube to the oil tankvia the cylinder-side second hydraulic lineand the tank-side second hydraulic line. Thus, when the operation switchis switched from the central sectionto the first section, the metal blockmoves forward (moves to the left in), which causes the movable hookto protrude below the pin receiver.

The second sectionconnects the tank-side first hydraulic lineand the cylinder-side second hydraulic lineand connects the tank-side second hydraulic lineand the cylinder-side first hydraulic line, to thereby send oil from the tank-side first hydraulic lineto the rod side of the tube of the hydraulic cylinder for a hookvia the cylinder-side second hydraulic line, and return oil from the base end side of the tube to the oil tankvia the cylinder-side first hydraulic lineand the tank-side second hydraulic line. Thus, when the operation switchis switched from the central sectionto the second section, the metal blockmoves backward (moves to the right in), which causes the movable hookto retreat from below the pin receiver.

The electrical systemof the present example is constituted by connecting the high voltage side of the first power supply linethat extends from the operation switchto the solenoid for a first sectionof the electromagnetic valve, and similarly connecting the high voltage side of the second power supply linethat extends from the operation switchto the second section solenoidof the electromagnetic valve, connecting the high voltage side of the shared power supply linethat bundles together the low voltage sides of the first power supply lineand the second power supply linethat extend from the solenoid for a first sectionand the second section solenoidto the tilt switch, and returning the low voltage side of the shared power supply linethat extends from the tilt switchto the operation switch. A power supplyis provided on the shared power supply line.

If the operation switchis operated when the tilt switchis in a state allowing the flow of current and a current is passed through the first power supply line, the solenoid for a first sectionis activated and the electromagnetic valveis switched from the central sectionto the first section, and the movable hookis caused to move forward. Further, if the operation switchis operated when the tilt switchis in a state allowing the flow of current and a current is passed through the second power supply line, the second section solenoidis activated and the electromagnetic valveis switched from the central sectionto the second section, and the movable hookis caused to retreat. With respect to all of the operations of the operation switch, if the tilt switchis not in a state allowing the flow of current, the electromagnetic valvecannot be switched, and the movable hookcannot be caused to move forward or to retreat.

Procedures for detaching the attachmentin the attachment attaching/detaching deviceof the present example will now be described. The tilt switchof the present example is designed so as to enter a state that cuts off the flow of current when the tilt switchis in a tilted posture in which one end that is connected to the shared power supply lineis at an angle of elevation (upward tilt angle) that is equal to or greater than the horizontal, and to enter a state that allows a flow of current when the tilt switchis in a tilted posture in which the one end is at an angle of depression (downward tilt angle) that is less than the horizontal. Further, when the center of gravity G of the attachmentattached to the attachment attaching/detaching deviceis on a side further away from the movable hookthan a position directly below the fixed hook, the tilt switchis attached to the side plateof the arm connection partin a tilted posture in which the one end is at an angle of depression (see).

In a state of procedurewhen starting the operation to detach the attachment, as illustrated in, the first pinof the attachmentis engaged with the fixed hook, and the second pinof the attachmentis engaged with the movable hookfrom below and sandwiched between the movable hookand the pin receiver, and there is no risk of the attachmentfalling off unless, for example, the hydraulic cylinder for a hookinadvertently causes the rod for a hookto retract. However, since the tilt switchis in a tilted posture with one end at an angle of depression (see the thin solid arrow in), in the state of procedure, it is possible to supply electric power to the electromagnetic valvethrough the electrical system.

From the state of procedurein which it is possible to supply electric power to the electromagnetic valvethrough the electrical system(see), when the operation switchis operated to supply electric power from the second power supply lineto activate the second section solenoid, the electromagnetic valveswitches the connection relationship from the central sectionto the second sectionto thereby send oil to the rod side of the tube of the hydraulic cylinder for a hookthrough the second hydraulic line for cylinder, and as illustrated in, the state of procedurein which the movable hookhas been retracted can be achieved (the movable hookis hidden by the side plateand is not shown).

In the state of procedure(see), the attachmentis a state in which the first pinis simply engaged with the fixed hook. However, because the center of gravity G of the attachmentis on a side that is farther from the movable hookthan a position directly below the center of the fixed hook, a rotational force (see the dashed outline arrow in) in a direction approaching the movable hookthat is centered on the first pinwhich is engaged with the fixed hookis imparted to the attachment, the second pinis pushed against the pin receiver, and the first pindoes not deviate in a direction away from the fixed hook, and thus there is no risk of the attachmentfalling off.

Here, when the hydraulic cylinder for an attachmentis actuated from the state of procedure(see) to cause the rod for an attachmentto retract, as illustrated in, the attachment attaching/detaching deviceis rotated so as to be raised upward (right rotation in; see the white outlined arrow), and the tilt switchenters the state of procedurein which one end is at an angle of elevation (see the thin dashed-line arrow in). The attachmentis rotated around the first pinengaged with the fixed hookin a direction that brings the center of gravity G closer to movable hook(right rotation in), and rotation of the attachmentis stopped at a stage when the center of gravity G is located directly below the center of the fixed hook, and thereafter only rotation of the attachment attaching/detaching devicewith respect to the attachmentwhich is fixed in position is continued.

In the state of procedure, because one end of the tilt switchis at an angle of elevation, it is not possible for the electrical systemto supply power, and an operation to move the movable hookforward or backward by operating the operation switchis restricted. This is to ensure that the movable hookdoes not inadvertently advance or retreat when subsequently detaching the attachmentcompletely from the attachment attaching/detaching device, and also to ensure that when attaching the attachmentto the attachment attaching/detaching deviceonce again, the movable hookcannot move forward unless the attachment attaching/detaching deviceis in a tilted posture in which the first pincannot come out from the fixed hook. Thus, work for attaching and detaching the attachmentis carried out in a safe state that prevents the attachmentfrom falling off.

From the state of procedure(see), when raising of the attachment attaching/detaching deviceis continued to place the attachment attaching/detaching devicein a tilted posture in which the fixed hookopens in the downward direction, as illustrated in, the first pinof the attachmentis released from the fixed hook, and the state of procedureis entered in which the attachmentis completely separated from the attachment attaching/detaching device. In this case, by placing the attachmenton the ground and then lifting the attachment attaching/detaching deviceupward, the risk of dropping the attachmentcan be eliminated. As described above, although the attachment attaching/detaching deviceof the present disclosure does not have a locking mechanism, the attachmentcan be safely detached simply by operating the operation switchof the electrical systemand changing the tilted posture of the attachment attaching/detaching device.