Information
-
Patent Grant
-
6253684
-
Patent Number
6,253,684
-
Date Filed
Tuesday, August 18, 199826 years ago
-
Date Issued
Tuesday, July 3, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
- Morano; S. Joseph
- Jules; Frantz F.
Agents
- Hovey, Williams, Timmons & Collins
-
CPC
-
US Classifications
Field of Search
US
- 104 1723
- 104 1724
- 104 1725
- 104 250
- 104 251
- 104 1722
-
International Classifications
-
Abstract
A stop mechanism for detaching a conveyor trolley from a drive system which normally drives the trolley along a conveyor track. A ramp can be moved into the path of a trolley dog so that the trolley dog moves upwardly along an inclined ramp surface to disengage the trolley dog from a drive dog carried by a driven chain of the conveyor system. The actuating mechanism for the ramp includes a pivotal cam plate actuated by a power cylinder. A cam slot in the cam plate receives a cam roller connected with a guide link which moves in a vertical guide slot. The guide link is connected with the ramp to move it up and down under the control of the actuating cylinder.
Description
FIELD OF THE INVENTION
This invention relates generally to conveyor systems and more particularly to an improved stop mechanism for detaching trolleys from the drive systems of large conveyor systems of the type commonly known as power and free conveyors.
BACKGROUND OF THE INVENTION
Automobile assembly plants and other facilities that require large conveyor systems often make use of power and free conveyors. A power and free conveyor includes a number of trolleys which travel along conveyor tracks and are equipped with carriers on which partially assembled automobile bodies or other articles are transported between successive work stations. The trolleys are normally propelled by a drive chain which travels continuously along a separate track on wheels connected with the chain. The trolley typically has a pivotal arm which includes a trolley dog. The trolley dog is normally engaged by a drive dog that projects from the chain so that the chain conveys the trolley along the conveyor track. In a commonly used conveyor system known as an inverted power and free conveyor, the drive chain is located below the trolley.
A power and free conveyor is advantageous in many applications because the drive chain runs continuously and all of the carriers are conveyed except for those that are selectively detached from the drive chain so that work can be performed on the objects they carry. Thus, some of the carriers can be stopped without the need to stop all of the others.
It is necessary to provide a power and free conveyor with a stop mechanism that is used to selectively disengage the trolleys from the drive chain so that the carrier can be stopped at the desired locations. Also, it is necessary to stop a carrier that is approaching a preceding carrier that is stopped on the track. Devices that perform the latter function and prevent collisions between carriers are known as accumulators. The present invention is concerned instead with a stop mechanism that may be situated at a selected location along the conveyor track and actuated to stop the next coming trolley adjacent to a work station.
Different types of stop mechanism have been proposed, mostly involving the insertion of a blade in the path of the trolley lever to pivot the lever in a direction to detach the trolley dog from the chain dog. Another type of stop is disclosed in U.S. Pat. No. 4,790,247 to Summa. The present invention is an improvement over all of the foregoing types of stop mechanisms.
Although the stops that have been proposed in the past operate in a satisfactory manner, they are not wholly free of problems. Most notably, the ability of prior stop mechanisms to function reliably over an extended operating life is questionable. Each time the stop mechanism is engaged or released, its parts are subjected to considerable wear which can cause a malfunction when the cumulative effective of the wear builds up to the point where the parts no longer cooperate as intended. If the stop mechanism fails, it is necessary to shut the entire conveyor system down long enough to allow the necessary repairs or replacement to be completed. This can create a significant problem because of the combined effect of the lost production and the costs that are involved in repairing or replacing the stop mechanism.
SUMMARY OF THE INVENTION
The present invention is directed to an improved stop mechanism which is specially constructed to function reliably and effectively over a prolonged operating life. In accordance with the invention, a pivotal cam plate is provided with a cam slot in which a cam roller operates. The cam roller is connected into a guide link that is restricted to up and down movement in a guide slot. The cam plate may be pivoted by a power cylinder to cause the cam to travel along the cam slot, and this in turn causes the guide link to move vertically in the guide slot.
The guide link forms part of a linkage between the cam mechanism and a ramp which is moved upwardly and downwardly with the guide link. When the ramp is lowered, it is located below the trolleys and does not effect their movement along the conveyor track. However, when the stop mechanism is actuated, the ramp is raised and then presents an inclined ramp surface in the path of the incoming trolley dog. The trolley dog travels upwardly along the ramp surface and pivots the trolley arm until the trolley dog has been raised far enough to detach from the chain dog. This stops the trolley until the ramp is lowered to allow the trolley dog to drop to a position at which it is engaged by the next incoming chain dog to transport the trolley away.
The use of a pivoting cam plate and cooperating cam and guide slots provides the stop mechanism with a smooth operating cycle which reduces the wear on the parts. At the same time, the ramp moves linearly up and down, so its motion is simple and repeatable. The overall result is a stop mechanism that is reliable, durable, safe, and economical, as well as applicable to both new and existing power and free conveyor systems.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:
FIG. 1A
is a fragmentary side elevational view of a portion of an inverted power and free conveyor system of the type that may be equipped with a stop mechanism constructed in accordance with the present invention;
FIG. 1B
is a fragmentary side elevational view similar to
FIG. 1A
, but showing the stop mechanism of the present invention actuated to detach a trolley of the conveyor system from the drive chain which normally conveys it along the conveyor track;
FIG. 2
is a fragmentary front elevational view of the trolley and related parts shown in
FIGS. 1A and 1B
;
FIG. 3A
is a fragmentary side elevational view on an enlarged scale showing the actuating mechanism and ramp included in the stop mechanism of the present invention, with the ramp in its lower position;
FIG. 3B
is a fragmentary elevational view similar to
FIG. 3A
, but showing the actuating mechanism in its actuated condition to move the ramp to its raised position for detachment of the trolley from the drive chain;
FIG. 4
is a fragmentary perspective view showing the actuating mechanism in a condition where the ramp is in its lowered position; and
FIG. 5
is a fragmentary perspective view similar to
FIG. 4
, but showing the actuating mechanism in its actuated condition to move the ramp to its raised position.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings in more detail and initially to
FIG. 1A
in particular, numeral
10
generally designates an inverted power and free conveyor of the type commonly used in automobile assembly plants and other applications. The conveyor
10
is used to convey partially completed automobile bodies or other workpieces which are carried on carriers (not shown). The carriers are mounted on a plurality of wheeled trolleys such as the trolley generally identified by numeral
12
. The trolleys
12
travel along spaced apart conveyor tracks
14
, and the trolleys in each set are connected with one another by a draw bar
16
or similar device. Each carrier is supported on two or more of the trollies
12
and is conveyed with its contents along the conveyor tracks
14
as the trollies travel along the tracks. The leading trolley
12
for each carrier has a rigid body
18
carrying two pairs of wheels
20
that roll along the tracks
14
. Guide wheels
22
are mounted on each trolley body
18
to turn about vertical axes to maintain the trolley properly centered on the tracks
14
.
The leading trolley for each carrier is provided with an accumulator mechanism which includes a pair of side plates
24
mounted above the trolley body
18
and equipped with an actuating lever
26
. The lever
26
is normally in the raised position shown in solid lines in
FIG. 1A
but can be pivoted downwardly to the broken line position when it engages the carrier of a preceding set of trolleys. This disconnects the trolley
12
from the drive system which normally propels it.
The trolley body
18
is provided with a pivot arm
28
which carries a retractable trolley dog
30
and a pivotal hold back dog
32
. The hold back dog
32
is pivotally mounted at
34
to the trailing end of the pivot arm
28
. The trolley dog
30
is spaced forwardly from the hold back dog
32
and has an inclined leading surface
30
a
. A horizontal pivot bolt
36
mounts the pivot arm
28
to the trolley body
18
and is located so that the weight of the arm
28
urges its trailing end downwardly.
Another set of tracks
38
are located generally below the conveyor tracks
14
and are used for guiding of a drive chain
40
which is used to transport the trolleys
12
along the conveyor tracks
14
. The lower tracks
38
may be mounted on supports
42
which are secured to the floor
44
or another surface of the building in which the conveyor system
10
is installed.
Wheels
46
which travel along the lower track
38
are connected by brackets
48
with the drive chain
40
. The chain
40
is equipped with a plurality of spaced apart drive dogs
50
which project upwardly from the chain
40
and are normally received between the trolley dog
30
and the hold back dog
32
. In normal operation, the chain drive dog
50
pushes against the back surface of the trolley dog
30
in order to drive the trolley
12
along the conveyor tracks
14
. The hold back dog
32
catches on the trailing surface of the drive dog
50
when the trolley
12
is traveling down-hill, thus preventing the trolley from overrunning the drive dog
50
.
As thus far described, the conveyor
10
has a conventional construction for the most part. The construction and operation of the conveyor system is illustrated and described more particularly in U.S. Pat. No. 4,790,247 to Summa which is incorporated herein by reference and which may be reviewed for a more detailed explanation of the construction and general operation of the trolley and the conveyor system. When the lever
26
of the accumulator device is pivoted downwardly to the broken line position of
FIG. 1A
due to engagement with a preceding carrier, the pivot arm
28
is pivoted in a counterclockwise direction as viewed in
FIG. 1A
to retract the trolley dog
30
upwardly so that it detaches from the drive dog
50
, thus stopping the trolley and preventing collisions between carriers.
The present invention is directed to a stop mechanism which may be installed at one or more selected locations along the conveyor system and which functions to stop the trolley
12
at a work station where work can be performed on the workpiece carried on the carrier.
Referring now more particularly to
FIGS. 3A and 3B
, the stop mechanism has a rigid frame which is generally identified by numeral
52
and which includes a flat side plate
54
and opposite end plates
56
and
58
extending from the side plate
54
. Brackets
60
are secured to the outside faces of tracks
14
and
38
and are secured to the end plates
56
and
58
by suitable fasteners
62
which mount the frame
52
to the tracks of the conveyor system. The side of the mechanism opposite plate
54
may be covered by a suitable cover plate (not shown).
The stop mechanism has an actuating system which includes a pivotal cam plate
64
. The cam plate
64
has an irregular shape that is generally triangular with rounded corner portions. One corner portion of the cam plate
64
is received between a pair of mounting lugs
66
which project from the end plate
56
of the frame. A horizontal pivot pin
68
connects the corner of cam plates
64
to the brackets
66
such that the cam plate can pivot about the horizontal axis provided by the pin
68
.
Pivotal movement of the cam plate
64
is effected by a pneumatic cylinder
70
having its base end pinned at
72
to a lug
74
projecting from the end plate
58
. The cylinder
70
has a piston rod
76
, the end of which is pinned at
78
to another corner area of the cam plate
64
. When the rod
76
is fully extended, the cam plate
64
is pivoted about pin
68
to its extreme counterclockwise position which is the position shown in FIG.
3
A. Retraction of the rod
76
pivots the cam plate
64
in a clockwise direction about pin
68
, and the cam plate is in the position shown in
FIG. 3B
when the rod
76
is fully retracted.
The cam plate
64
is provided with a cam slot
80
which extends from a bottom end located between the pins
68
and
78
to an upper end portion which is located near the third corner area of the cam plate
64
. The opposite edges of the slot
80
are generally parallel to one another. The left edge of slot
80
(as viewed in
FIG. 3A
) is provided near its top end portion with an inward projection
82
which forms a shoulder
84
adjacent to the projection
82
in the upper end portion of the slot
80
. As will be explained more fully, the projection
82
and shoulder
84
serve a locking function for the stop mechanism.
A cam element for the actuating system includes a cam roller
86
which is mounted on a horizontal bolt
88
. The cam roller
86
is received in the cam slot
80
and has a diameter to fit closely between the opposite edges of slot
80
.
The end of the bolt
88
opposite the end carrying the cam roller
86
is connected with the lower end of a guide link
90
. The guide link
90
is closely received in a vertical guide slot
92
formed in the side plate
54
of the frame
52
. The link
90
is restricted to vertical movement upwardly and downwardly within the guide slot
92
.
The upper end of the link
90
is connected by a horizontal screw
94
with a ramp
96
. The ramp
96
has an inclined ramp surface
96
a
which faces an approaching trolley
12
traveling in the forward direction indicated by the directional arrow
98
in FIG.
1
B. The ramp
96
is restricted to up and down movement by a key
99
(FIGS.
3
A and
3
B).
In operation of the conveyor system
10
, the pneumatic cylinder
70
is normally maintained with its rod
76
fully extended as shown in FIG.
3
A. The cam plate
64
is then in a pivotal position where the lower end of its cam slot
80
is aligned with the lower end of the guide slot
92
. Consequently, the cam roller
86
is located in the lower end portion of the cam slot
80
and the guide link
90
is in its lowermost position in the guide slot
92
. This locates the ramp
96
in its lowermost position which is the position shown in FIG.
3
A. In this position, the ramp
96
is located well below the trolley dog
30
and all other portions of the pivot arm
28
. The trolley
12
thus bypasses the ramp
96
.
When it is desired to stop one of the carriers at the work station adjacent to the location of the stop mechanism, the cylinder is actuated to retract its rod
76
. This pivots the cam plate
64
in a clockwise direction from the position shown in
FIG. 3A
to the position shown in FIG.
3
B. As the cam plate
64
pivots in a clockwise direction, the cam slot
80
moves about the pivot arm
68
, and the cam slot
80
comes into alignment with progressively higher portions of the vertical guide slot
92
. Because the cam roller
86
is restricted to movement within the cam slot
80
and the guide link
90
is connected with the cam roller
86
and is restricted to movement within the guide slot
92
, the cam roller
86
is moved progressively upwardly in the cam slot
80
and the guide link
90
is moved progressively upwardly in the guide slot
92
. The ramp
96
is connected with the guide link
90
and moves upwardly with upward movement of the guide link.
The result is that the ramp
96
is moved upwardly to the fully raised position shown in
FIG. 3B
(and also in FIG.
1
B). In this position, the cam roller
86
is seated on the shoulder
84
which is then located directly beneath the cam roller. This seating of roller
86
on shoulder
84
serves to lock the cam roller in place to prevent it from becoming displaced by the forces acting on it. As the trolley
12
approaches the raised ramp
96
, the pivot arm
28
comes into contact with the inclined ramp surface
96
a
, and the inclined surface
30
a
of the trolley dog
30
rides upwardly along the ramp surface
96
a
. This causes the pivot arm
28
to pivot in a counterclockwise direction about the pivot pin
36
, and the retractable trolley dog
30
is retracted upwardly far enough that it is disengaged from the chain drive dog
50
. The drive dog
50
then passes beneath the trolley dog
30
and no longer provides driving action for the trolley
12
. The trolley thus stops at the work station so that work can be performed on the article carried on its carrier.
It is noted that the chain
40
continues to travel and to convey other trolleys in the system along the conveyor tracks
14
. Consequently, the remaining carriers can continue to be conveyed as desired.
When it is desired to move the trolley
12
away from the work station, the cylinder
70
is actuated to extend its piston rod
76
. This pivots the cam plate
64
in a counterclockwise direction from the position of
FIG. 3B
to the position of
3
A. The cam slot
80
progressively comes into registration with lower parts of the guide slot
92
, and the cam roller
86
and the guide link
90
thus move downwardly until the position of
FIG. 3A
is reached. At this time, the ramp
96
is in its lowermost position, and the trailing portion of the pivot arm
28
moves downwardly under the influence of gravity to the position shown in FIG.
1
A. Then, the next incoming chain dog
50
can engage the hold back dog
32
and pivot it upwardly so that the chain dog
50
can enter the space between dogs
30
and
32
and come into engagement with the trailing edge of the trolley dog
30
. The chain then conveys the trolley
12
away from the work station and along the conveyor tracks
14
.
From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.
Claims
- 1. A stop mechanism for a conveyor system having a trolley riding on a track and including a trolley dog normally engaged by a drive dog of a drive member to propel the trolley along the track, said stop mechanism comprising:a frame; a ramp member mounted on said frame for movement between a first position wherein an inclined ramp surface of said ramp member is positioned in the path of said trolley dog to engage the trolley dog and disengage it from said drive dog, and a second position wherein said trolley dog can pass said ramp member; a cam plate mounted on said frame for pivotal movement, said cam plate having a cam slot therein; a cam element received in said cam slot for movement therein when said cam plate is pivoted; a power actuator connected to pivot said cam plate to effect movement of said cam element in said cam slot; a connection between said cam element and ramp member effective to move said ramp member between the first and second positions thereof in response to movement of said cam element in said cam slot, a guide slot in the frame; and a guide member received in said guide slot for movement therein, said guide member being connected with said cam element for movement in the guide slot in response to movement of said cam element in the cam slot, said guide member being connected with said ramp member to effect movement thereof between said first and second positions in response to movement of said guide member in said guide slot.
- 2. A stop mechanism as set forth in claim 1, wherein said guide slot has a substantially vertical orientation and said ramp member has a substantially vertical and linear path of movement between the first and second positions thereof.
- 3. A stop mechanism as set forth in claim 2, wherein said guide member comprises a guide link having a lower end portion connected with said cam element and an upper end portion connected with said ramp member.
- 4. In a power and free conveyor system of the type having a track, a trolley riding on the track to convey workpieces along the track, a pivot arm on the trolley carrying a trolley dog, and a drive member carrying a drive dog normally engaged with the trolley dog for conveying the trolley, a stop mechanism comprising:a frame; a ramp member mounted on said frame for substantially vertical movement between first and second positions, said ramp member having an inclined ramp surface which is situated in the first position of the ramp member in the path of said trolley dog and oriented to effect pivoting of said pivot arm in a direction to disengage said trolley dog from said drive dog, said ramp member in the second position thereof being situated to allow movement of said trolley dog past said ramp member; a cam plate mounted for pivotal movement on the frame and having a cam slot; a substantially vertical guide slot in said frame located such that different portions of said cam slot and guide slot are aligned as the cam plate pivots; a cam element received in said cam slot for movement therein; a guide member received in said guide slot for movement therein and connected with said cam element such that the cam element and guide member occupy aligned portions of the cam slot and guide slot, respectively; a connection between said guide member and ramp member effective to move the ramp member between said first and second positions as said guide member moves in said guide slot; and a power actuator connected to selectively pivot said cam plate.
US Referenced Citations (12)