JPH0419133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic conveyance system, and more particularly, the present invention relates to an automatic conveyance system that has a downwardly inclined guide member, a free running carrier that is placed on the guide member and runs, and further has a downwardly inclined The present invention relates to an automatic transport system equipped with a guide member and a device for restricting the forward movement of a carrier on a non-inclined guide member.

The automatic transport systems to which this invention relates are used in garment manufacturing plants to transport workpieces to a series of processing stations or to storage areas where various operations are processed. This type of conveyance system is disclosed in Japanese Patent Application Laid-open No. 145024/1983, which can be referred to as part of this invention. The system is highly automated and comprises a free-running trolley for holding the workpiece and a rail network on which the trolley rests, the rail network consisting of a main rail and a subordinate rail loop section,
The main rail guides the trolley to the subordinate rail loop, which guides the trolley to or from the processing station or serves as a storage area. The rail network further includes an endless traction chain adjacent to the main rail, pushers mounted at intervals along the chain that engage the trolley to propel the trolley along the main rail, and pushers that engage the trolley to propel the trolley along the main rail. - Equipped with a branch switch for transferring to the loop section and from the loop section to the main rail.

Each slave loop section has a gap adjacent to the main rail, the main rail likewise has a gap adjacent each slave loop section, and a corresponding diverter switch consists of a short section of rail and an actuating device for actuation. The apparatus is for moving the rail section from a first position bridging a gap in the main rail to a second position bridging a gap in the subordinate loop section and vice versa. To transfer a trolley from the main rail to the slave loop section, the rail section is first positioned within the gap of the main rail to receive the trolley propelled by the pusher. Thereafter, the actuator moves the rail section with the trolley received into the gap in the slave loop, and the trolley is propelled by the pusher onto the rail of the slave loop.

Other trolley-rail systems include a main rail and a slave loop section, a diverter switch adjacent each slave loop section, a free-running trolley that rides on the rail, and a trolley pusher. Each diverter switch consists of a pair of pivoting fingers with an axis of rotation on the main rail; when both fingers are closed, the trolley is guided along the main rail over the diverter switch; When opened, the trolley is guided towards or ejected from the slave loop.

In both of the trolley-rail systems described above, a computer is used to control the circulation of the trolleys to the slave loops, and is also used to control their corresponding branch switching mechanisms. In order to perform a proper branch switching operation, the movement of the branch switch must be timed with the arrival of the selected trolley, and the computer primarily calculates the trolley's position from the location of the pusher. In these or other types of diverter switches, there are always discontinuities in the main rail or slave loop that can cause the trolley to inadvertently fall off the rail network. .

A dependent loop used as a storage area is preferably placed several feet above the floor to provide work space, with the space below the storage loop used for processing stations, other storage areas, walking paths, or other purposes. can do. In this case, at least a portion of the rail network is tilted upward;
At least a portion slopes downward. Moreover, this type of automatic transport system may be arranged to occupy two floors of a factory. In this case, at least a portion of the rail network slopes upward and at least a portion slopes downward, connecting the two floors. When a free-running, unrestrained trolley travels on a downwardly sloping section of such a rail network, the trolley rolls in front of the pusher and rolls along the sloping rail section to the rear of the previous pusher. 3 to 5 feet downward (0.91 to
1.52m) descend. If there is a downwardly sloping rail section immediately upstream of the diverter switch intended to divert the trolley, and the pusher is unable to catch up with the trolley before reaching the diverter switch, the computer will The trolley would pass through the branch switching mechanism before moving the branch switch to the slave loop section, rendering the switching operation ineffective. Furthermore, in the system of the above-mentioned Japanese Patent Application Laid-open No. 61-145024,
A planned trolley malfunction causes the trolley immediately in front of it to divert into the dependent loop section, and the malfunctioning trolley falls off the rail through the gap created when the switching mechanism attempts to switch the trolley. or a malfunctioning trolley may be inadvertently diverted to an unscheduled processing station or storage area.
Or it may cause jamming in the system.

In addition to the downward slope of the rail section, there are other factors that can cause the trolley to advance in front of the pusher or cause the problems described above. For example, air flowing in through an open door or window
Like wind acting on a sail, it will act on clothing suspended from a trolley, or people may inadvertently touch the trolley or associated workpieces, or the operator may inadvertently load the trolley onto the rail. You may end up pushing the trolley forward without being careful.

Accordingly, a principal object of the present invention is to have a free-running carrier, a guide member for the carrier, and a pusher for the carrier, wherein the carrier, when propelled forward by gravity or other external force, An object of the present invention is to provide an automatic conveyance system that does not allow large forward advances.

A particular object of the invention is to provide an improvement in the device which is simple in construction and use and which substantially interferes with the circulation of the carrier within the system.

Other objects and advantages of the invention will become apparent from the following detailed description and accompanying drawings.

The present invention relates to a restraining means in a conveying system of the type comprising a number of free-running carriers, guide members for the rear carriers, and means for propelling the carriers along the guide members. According to one feature, the propulsion means comprises an endless traction chain and a pusher projecting from the chain to drive the carrier, and the restraining means comprises a number of brackets projecting downward from the chain, a bracket located in front of each pusher. limits the carrier accommodating section for receiving carriers. According to another characteristic of the invention, each bracket has a restriction within a restriction section defining a loading position for introducing the carrier into the carrier receptacle and a restraining position for preventing the carrier from escaping from the receptacle. Rotatably attached to the chain.

According to another feature of the invention, each restraining bracket is removably attached to the chain.

In the present invention, the stop bracket allows the workpiece carrier or trolley to pass rearward past the stop bracket from the front, but prevents the trolley from passing forward past the stop bracket from the rear, so that each The pusher and the trolley that cooperates with it are not separated by more than a predetermined distance, and the pusher and the trolley are separated by a large distance at the branch switch, causing the trolley to fall or malfunction, and the trolley to gather in one place, causing jamming. is prevented.

In the present invention, the head of the restraint bracket has a recess extending inwardly to receive the horizontal pin and terminating in a throat, the throat being a generally downward bearing pivotally engaged to the horizontal pin. The restraining bracket may include a surface, the head being manually movable upwardly relative to the horizontal pin along the recess, such that the restraining bracket is removable from the horizontal pin and the chain. When necessary or desirable, the chain can be quickly installed without the need for tools or the need to disassemble the chain. And when the restraint bracket is not needed, it can be easily and easily removed from the chain. The invention therefore allows the same chain to be used in conveying installations with different or varying requirements for restraint brackets.

Referring now to the drawings, FIG. 1 shows an automatic transport system according to the present invention, generally indicated by the reference numeral 5. In FIG. This system includes a master computer 8, a propulsion track 10 having pushers 15, 15 projecting downward, a motor drive unit 3 of the propulsion track, a main rail 12 disposed below the propulsion track 10, and a propulsion track 10 having pushers 15, 15 projecting downward. A free-running trolley 1 mounted on a trolley 1 and propelled by pushers 15, 15
4, 14, and subordinate loop sections 16, 16, 32, 3 arranged along the main rail, some of which are in pairs.
2, 17 and 19. Each of these dependent loops 16, 16 and 32, 32 leads to a processing station 33 or 35. The dependent loop sections 17 and 19 are used for storage. Furthermore, the automatic conveyance system includes a pair of three-way branch switches 25, 25 for directly circulating the trolley between the main rail and each pair of dependent loop sections or between a predetermined pair of dependent loop sections. Two-way branch switches 27, 27 for circulating the trolley between the main rail and the dependent loop section or branch rail 31 that is not connected
and. Although the system shown in FIG. 1 includes a total of nine dependent loop sections, the number of loop sections could easily be varied as desired.

FIG. 2 shows a part of the automatic transport system 5 of FIG. 1, showing a main rail 12, a propulsion track 10 disposed above the main rail, and a pair of dependent loop parts 16 and 32. . One trolley 14a rests on the main rail 12 and one of the pushers 15 15
Propelled by a. The pusher 15a is on orbit 1
One of a series of pushers equally spaced along 0 and projecting downwardly from the track. The pusher 15a itself is driven by an endless traction chain (FIGS. 8 and 9) located within the overhead propulsion track 10, and as shown in FIG.
Move it towards 6. Series of restraint brackets 7
0,70 also project downwardly from the track 10, each bracket being located forward of each pusher 15,15. The dependent loop portion 16 includes a loop rail 28, a stop portion 38, and an elevator 54, with the opposing dependent loop portions 32 being mirror images of the loop portion 16.

The main rail 12, the subordinate loop section 16 and the subordinate loop section 32 each have a gap laterally parallel to each other, and the diverter switch 25 consists of a linear section 24 of the rail and an actuating device 18 controlled by the computer 8. . Main rail 12, rail division 2
4 and the loop-shaped rails 28, 30 are preferably formed of pipes. The actuator 18 moves the rail section 24 into a first position bridging a gap in the slave loop section 16 (the position shown), in a second position bridging a gap 29 in the main rail 12, and in a second position bridging a gap 29 in the slave loop section 32. a third bridging gap (not shown);
It acts to move laterally between the positions of.

In switching the trolley from the main rail to the slave loop section 16, the rail section 24 is first located in the gap of the main rail, and one of the pushers 15 advances the trolley from the main rail 12 onto the rail section 24. The computer then activates the actuator 18 to move the rail section 24 into the gap of the dependent loop section 28. When the trolley is positioned on the rail section 24, the pusher 15 continues to engage the trolley due to its wide width, and when the rail section reaches the gap of the dependent loop section 16, the pusher moves the trolley into the looped rail 28. Push forward to section 36. Actuator 18 then returns rail section 24 to main rail 12. Other trolleys can therefore run along the main rail or can also be switched by rail stations.

The looped pipe 28 of the dependent loop section 16 slopes downwardly from the insert 36, and the trolley rolls along the pipe under its gravity. A stop portion 38 is provided approximately in the middle of the loop-shaped rail 28, and the stop portion includes an upstream gate and a downstream gate (both not shown). The stop portion 38 stops the trolleys 14b-d at the upstream gate as shown, with the trolley 14b being located at the forefront of the line. The trolley 14b is
The upstream gate is closed until the operator 42 handles the trolley 14e and presses a button on the control panel 50 to open the upstream gate of the stop 38 and roll the trolley to the downstream gate located at the bottom of the stop. Wait at . This downstream gate is adjacent to the operator handling trolley 14e.

The operator 42, as shown in FIG.
The sewing machine 45 is used to sew the processed material 46 suspended from the trolley 14e. When all the processed materials suspended on the trolley have been processed,
The operator opens the downstream gate of the stop section 38 by pressing a button on the control panel 50, and the trolley 14e is moved to the elevator 54 by gravity.
Roll it towards the top. Another stop is provided at the bottom of the elevator so that the trolley can stop on main rail 1.
The trolley is held there while waiting to change direction to be reloaded on board 2. When the master computer detects the absence of a trolley on the rail section 24 and on the portion of the main rail 12 immediately upstream of the rail section 24, the computer activates the actuator 18 to move the rail section 24 into the slave loop section 16.
Then, the elevator 54 and its stop are started, and the trolley is placed in the elevator car. This truck consists of a track section 57 having a slot for receiving a trolley. The computer then operates the elevator to raise the trolley. The trolley 14, designated 14f in FIG. 2, is in the process of being raised. Then, after the trolley reaches the top of the elevator 54, the next pusher pushes the trolley out of the slotted track section 57 and onto the rail section 24.

In one form of operation, the computer activates the actuator 1 after the rail section 24 has received the trolley.
8 is actuated to pull the rail section 24 back onto the line of the main rail 12. The trolley returns to the main rail 12 while being pushed a little and moves downstream along the line. The trolley is then transported to the next loop section and its processing station.

FIG. 3 shows that dependent loop portions 17 and 19 are located at a substantially higher position relative to dependent loop portion 16 and its processing station, e.g.
The diagram shows lines placed at a foot (2.44 m) high position. This serves to secure processing space. The storage loop and storage trolley and workpiece 50 are raised sufficiently to allow people to walk and work below them, to place other workpieces or equipment, or to perform other tasks. make it possible to A downwardly sloping portion 90 of rail 12 communicates from dependent loop portion 19 to dependent loop portion 16 .

FIG. 4 shows a rear view of the trolley 14, indicated at 14n, the pusher 15c engaging the trolley 14n, and the stop bracket 70. Trolley 1
4n has two wheels 144 and 146 that rest on one of the rails of system 5. This wheel is attached to the inner surface of the hook-like upper part 141 of the trolley and straddles and balances on the rail. A T-shaped member 66 is formed at the top of the trolley 14n, and this member becomes the part that actually engages with the pusher 15c. pushsia 1
5c has an inverted T shape and extends downward from the inside of the propulsion track 10 behind the trolley (with respect to the traveling direction of the trolley on the main rail), and an endless traction chain 150 is disposed inside the track. be done. A pusher 15c is attached to this chain and pulled by the chain. A restraining bracket 70 is similarly attached to and pulled by the chain 150, and this bracket 70 is attached to the trolley 1.
It is located in front of 4n.

Next, considering the present invention, FIGS. 5, 6 and 7 illustrate a restraining bracket 70 which is made of metal or synthetic resin and includes a stem portion 72, a neck portion 74, a throat portion 79, Back part 82
and a curved head portion 76 having a pivot recess 78. An example of bracket 70 is made of cast aluminum and has the following dimensions:

A=0.25in (0.635cm) B=3.25in (8.255cm) C=2.594in (6.589cm) D=0.2in (0.508cm) E=1.625in (4.128cm) F=0.220in (0.559cm) G= 0.913in (2.319cm) H=0.310in (0.787cm) (Diameter) I=1.0in (2.54cm) J=0.332in (0.843cm) (Diameter) K=30° L=0.563in (1.430cm) (Radius ) M=0.312in (0.792cm) N=1.625in (4.128cm) O=9° P=0.188in (0.477cm) Q=0.563in (1.430cm) R=0.125in (0.317cm) (Radius) Furthermore, The vertical distance between the chain 150 and the rails 12, 24 is such that the brackets just reach below the corresponding T-shaped member 66 of the trolley 14 when the brackets are suspended from the chain.

8 and 9, the chain 150 and restraint brackets 70, 70 of the propulsion track 10 are illustrated.
Chain 150 has links 170, 170 and 17
2,172, the link 170 is the horizontal pin 1
76 and a vertical pin 178 to the link 172 to allow relative vertical and horizontal rotation for following the path of the main track 10. The chain 150 further includes shafts 80, 80.
The chain includes vertical wheels 180, 180 mounted on and horizontal wheels 182, 182 mounted on axles 184, 184 which guide the chain along the main track 10. The bracket 70 is removably attached to the horizontal shaft 80 of the chain by a snap fit at the throat 79 with the pivot recess 78 engaging the horizontal shaft 80, and the bracket cannot be rotated on the shaft. It is possible. Since the bracket 70 has the shape and dimensions described above, the bracket is balanced so that the stem portion 72 is at an angle of approximately 45° with respect to the horizontal plane, as shown in FIG. .

In the illustrated example, one of the brackets 70, 70 is mounted in front of each associated pusher;
Their separation distance is approximately 8in (20.32cm). This space defines a trolley storage area 86, which allows many spaces to accommodate one trolley, but is short enough that a computer can reasonably detect the presence of a trolley. .

The bracket 70 can be rotated rearward (counterclockwise) to the trolley loading position, and in that position, the stem portion 72 is oriented substantially horizontally and the chain 1
50 links 82 are touched. The bracket can then be rotated forward (clockwise) to the trolley restraining position, in which the stem portion is oriented substantially vertically and the back portion 82 of the head portion 76 is aligned with the spacer 84.
come into contact with. To load the trolley into the trolley receptacle 86, the trolley is inserted directly onto the rail section within the receptacle or onto the rail section in front of the associated stop bracket 70. At this time, the trolley remains in that position, and when the bracket 70 passes over the trolley, the bracket pivots upward to the trolley loading position and stores the trolley in the storage section. Alternatively, the trolley slides rearward, contacts the bracket and pivots the bracket upwards into the receptacle. Further, when the trolley is stopped on the rail and waits for the next bracket 70 to arrive, when the bracket 70 reaches the trolley, the bracket pivots upward to accommodate the trolley. The inertia of the trolley is large enough so that the brackets can accommodate the trolley without pushing it forward, and the 45° balanced tilt of the brackets ensures that the trolley can be accommodated from its initial position in front of the brackets, as described above. facilitates insertion of the trolley into the section.

In FIG. 10, a dependent loop section 16 indicated by 16s is shown.
A downwardly inclined portion 90 of the rail 12 that communicates with
is illustrated to illustrate one function of the restraining brackets 70,70. Trolley 14o rests on an inclined rail section 90 and rolls under the force of gravity in front of pusher 15o toward bracket 70o. The bracket 70o is connected to the slope of the rail portion 90 and the trolley 1.
Due to the weight of 4o, it rotates slightly forward to the trolley restraining position. If bracket 70o were not present, trolley 14o would continue rolling to the rear of pusher 15p. Trolley 14q is shown positioned at the entrance to horizontal portion 92 of rail 12 and already communicates with sloped portion 90. Shortly before that, trolley 14q hit restraint bracket 7.
0q, and when the trolley 14q reaches the entrance of the horizontal section 92, its momentum causes the trolley 14q to push the pusher 15.
Keep it slightly in front of q. After that, trolley 14
q dissipates its momentum and becomes a bracket 70q
It gradually retreats and re-engages with the pusher 15q. The figure shows a state in which the pusher 15, indicated by 15r, catches up with the trolley 14, indicated by 14r, and re-engages with it.

In order to secure machining space, the dependent loop section 16 and the machining station 33, indicated at 16s, are located near the bottom of the inclined rail 90.

Assuming that the trolley 14r is program-controlled to be transferred to the loop section 16s, the pusher 15r is connected to the rail section 2 of the diverter switch 27.
Immediately after communicating the upstream ends of 4, the computer activates the actuator 18 to transfer the rail section 24 to the gap in the dependent loop section 16s. pushsia 1
The distance from 5r to bracket 70r plus the distance the pusher moves forward during the lateral transfer of the trolley is less than the length of rail segment 24, so that the trolley does not move on rail segment 24 during the switchover. The trolley is maintained in the trolley storage section 8.
No matter where you are within 6, you will not advance forward beyond the rail section.

If the restraining bracket 70r were not attached, the trolley 14r would leave far in front of the pusher 15r and roll onto the rail section 24 before the pusher 15r reached it, and the trolley would then move too far in front of the pusher 15r and roll onto the rail section 24 before the pusher 15r reached it. Note that the entire switching operation would be avoided if it were not stopped by the corrugations 71 provided. Also, if there is no bracket 70q, the trolley 14
q will continue rolling to the rear of pusher 15r. Then, when the rail section 24 moves laterally to switch the trolley 14r, the trolley 14q falls from the main rail through the gap where the rail section 24 does not exist, and the branch switch 2
7 will cause jamming.

After the trolley 14r circulates around the looped rail 28 of the dependent loop section 16s, it is transported upwardly by the elevator 54 to the rail section 2.
4 and is pushed onto the rail section 24 by the next pusher and transferred towards the main rail. Brackets 70 associated with the pushers are located forward of the pushers so that when the rail sections 24 reach the line of the main rail, the trolleys can be received in their respective trolley receptacles 86 and advanced downstream. , or laterally transferred to the slave loop section 18 in response to a computer command.

At the top of the elevator, when the trolley first engages the pusher 15, it hits the front of the pusher along the rail section 24 or rolls forward by gravity on the rail section 24 due to an inadvertent tipping. there's a possibility that. The corrugations 71 on the rail section 24 stop the trolley before it falls off the rail section. When the rail section 24 reaches the line of the main rail, if the trolley 14 passes 8 inches (20.32 cm) in front of the pusher.
If it were to roll, the trolley would impact the bracket 70 laterally. However, due to the tilting of the stem portion 72 of the bracket 70, the bracket will normally pivot upwardly to accommodate the trolley. Additionally, when the trolley hits the bracket, the trolley will rest slightly tilted on the rail section 24 until the bracket 70 advances forward in response to the forward movement of the chain 150, and then enters the trolley receptacle. . If the trolley rolls more than 8 inches in front of the pusher, the trolley will be located in front of the restraint bracket, but will soon be automatically retracted. At this time, the bracket 70 can reliably overtake the trolley due to the corrugated portion 71.

While a restraining bracket for an automatic conveyance system has been described above as embodying the present invention, the invention may be otherwise described without departing from the scope thereof.
Various modifications and changes can be made. For example, if desired, the bracket 70 could be made integral with the chain, in which case the bracket 70
0 cannot be quickly attached to or removed from the chain. Additionally, if the bracket 70 is utilized with a trolley having a vertically narrow top end instead of the wide T-shaped member 66, the distal end of the stem portion 72 of the bracket 70 will be wide in the shape of an inverted T. It can also be formed. Also, bracket 7
It is also possible to form an inclined surface on the side edge of the stem portion 72 of 0, and in this case, the trolley can
2, this ramp facilitates upward pivoting of the bracket to accommodate the trolley in the receptacle 86. Furthermore, the restraining brackets 70, 70 can also be used in rail networks with sloped sections connecting two floors. Therefore, the present invention is disclosed by way of illustration and not by way of limitation.

[Brief explanation of drawings]

Figure 1 is a top view of an automatic conveyance system that utilizes the present invention, Figure 2 is a perspective view of a portion of the automatic conveyance system shown in Figure 1, and Figure 3 is a side view of another portion of the automatic conveyance system shown in Figure 1. Figure 4 is a rear sectional view of the trolley, propulsion track, restraint bracket, and pusher of the automatic conveyance system in Figure 1, and Figure 5 is a rear sectional view of the automatic conveyance system in Figure 1.
Figure 6 is a side view of the restraining bracket of the automatic conveyance system, Figure 6 is a top view of the bracket in Figure 5, and Figure 7 is a top view of the bracket in Figure 5.
The figure is an end view of the bracket in Figure 5, and Figure 8 is an end view of the bracket in Figure 1.
FIG. 9 is a side view of a part of the chain in the propulsion track of the automatic conveyance system shown in FIG. 5, and also shows the restraining bracket shown in FIG.
The figure is a side view of a downwardly inclined portion of the rail network of the automatic conveyance system of FIG. 1. Explanation of symbols, 5... Automatic conveyance system, 10...
...Propulsion track, 12...Main rail (guide means),
14...Free running trolley (carrier), 15...
... Pusher, 16, 17, 19, 32 ... Dependent loop section, 25, 27 ... Branch switch, 33, 3
5... Processing station, 46... Processing material, 7
0...Stopping bracket, 72...Stem part, 76
...Head part, 78...Recessed part, 79...Groat part,
150...Chain.

Claims (1)

[Scope of Claims] 1 Automatic conveyance equipment, including a rail 12, a number of freely movable work piece carriers 14 mounted on the rail, a chain 150 for propelling the work piece carriers along the rail, a restraining bracket 70, and a restriction means, the chain 150 including a plurality of pushers 15 for engaging the workpiece carriers 14 and a horizontal pin 80 extending across the chain, the horizontal pin 80 being spaced forwardly from each of the pushers. , a stop bracket 70 is pivotally suspended from each of the horizontal pins 80 such that one pusher 15 cooperates with the stop bracket 70 so that the workpiece carrier 14 moves rearwardly past the stop bracket 70.
and thereafter prevent the workpiece carrier 14 from moving forwardly past its stop bracket 70, which
It has a curved head 76 and an elongated stem portion 72 extending downwardly from the head into the path of the workpiece carrier 14, with the head 76 extending inwardly to receive a horizontal pin 80 and having a throat 79. terminating in a recess 78 , the throat 79 has a generally downward bearing surface pivotally engaged with the horizontal pin 80 , and the head 76 is manually rotated upwardly along the recess 78 relative to the horizontal pin 80 . movable so that the restraining bracket 70 is removable from the horizontal pin 80 and the chain 150, the restricting means accommodating a pivoting movement of the restraining bracket 70 relative to the chain 150 to a forward pivoting movement of the stem portion 72; The limiting means restricts the chain 1 in front of the horizontal pin 80.
50 and a spacer 84 on top of the spacer 84.
engages the stem portion 72 at a point located along the length of the stem portion 72 between the point of the stem portion 72 engaged by the workpiece carrier and the horizontal pin 80; The force acting on 72 tends to pivot stem portion 72 about spacer 84, forcing the bearing surface of throat 79 into engagement with horizontal pin 80, thereby causing stop bracket 70 to pivot. Automatic conveyance equipment characterized by being prevented from separating from the horizontal pin 80. 2. An automated conveyance system according to claim 1, wherein each stop bracket 70 is made of plastic, and the recess 78 of each stop bracket 70 includes a horizontal pin that receives the stop bracket 70 at one point along its length. having a width less than a diameter of 80 mm;
An automatic conveying installation characterized in that the restraining bracket 70 thereby has a snap action when it is installed onto the horizontal pin 80 and when it is removed from the horizontal pin 80.