US3767072A

US3767072A - Warehousing system with latch mechanism for elevator

Info

Publication number: US3767072A
Application number: US00249946A
Authority: US
Inventors: W Atwater
Original assignee: Triax Co
Current assignee: Triax Co
Priority date: 1972-05-03
Filing date: 1972-05-03
Publication date: 1973-10-23
Anticipated expiration: 1990-10-23

Abstract

An automatic warehousing system including a mechanized load carrier having a vertically movable elevator portion and embodying latch mechanism adapted to automatically hold the elevator portion adjacent the upper section of the load carrier and prevent it from moving downwardly toward ground level, in the event that the elevator portion inadvertently moves upwardly beyond the normal safe travel limits. A cushioning device is also provided for cushioning impact of the elevator with the upper section of the load carrier structure so as to aid in preventing material distortion and destruction of the component parts of the load carrier, in the event of the aforementioned inadvertent movement of the elevator portion beyond its normal upper limit of travel.

Description

United States Patent 1 Atwater Oct. 23, 1973 [75] Inventor: WayneG.Atwater,Willoughby,

Ohio

[73] Assignee: The Triax C0mpany,Cleveland,

Ohio.

[22] Filed: May 3, 1972 [21] Appl. No.: 249,946

3,593,862 7/1971 Pierson 214/11 R FrimarYTk amineF-GeraIJ Forlen za Assistant Examiner-R. B. Johnson Attorney-George S. Baldwin et al.

[57] ABSTRACT An automatic warehousing system including a mechanized load carrier having a vertically movable elevator portion and embodying latch mechanism adapted to automatically hold the elevator portion adjacent the upper section of the load carrier and prevent it from moving downwardly toward ground level, in the event that the elevator portion inadvertently moves upwardly beyond the normal safe travel limits. A cushioning device is also provided for cushioning impact of the elevator with the upper section of the load carrier structure so as to aid in preventing material distortion and destruction of the component parts of the load. carrier, in the event of the aforementioned inadvertent movement of the elevator portion beyond its normal upper limit of travel.

14 Claims, Drawing Figures WAREHOUSING SYSTEM WITH LATCH MECHANISM FOR ELEVATOR This invention relates in general to automatic warehousing systems including a mechanized load carrier having an elevator portion, for transporting loads to and from a storage rack and relates more particularly to a novel arrangement oflatch mechanism for use with the load carrier, for positively holding the elevator at an upper position in the event that it inadvertently moves upwardly beyond its normal range of travel.

BACKGROUND OF THE INVENTION A warehousing system of the general type to which the present invention may be applied but by no means the only such system is disclosed in assignees U. S. Pat. No. 3,l 39,994 issued July 7, 1964 in the name of Anthony R. Chasar, and entitled Mechanical Load Handling, Transfer and Storage Equipment. Such patented warehousing system comprises a storage frame or rack having vertically and horizontally arranged storage volumes opening at a vertical work face disposed alongside an adjacent aisle or travel zone. An automatically controlled mechanized load carrier is movable along the aisle or travel zone, and such load carrier conventionally comprises a horizontally movable conveyor portion which travels alongside the storage frame and provides vertical track means for an elevator portion capable of delivering loads to different levels in the storage frame. The elevator portion carries a laterally extensible extractor mechanism for inserting loads into and retrieving loads from the selected storage volume. In order to attempt to prevent inadvertent movement of the elevator portion of the load carrier up beyond a predetermined maximum desired height, such warehousing systems may include safety devices, such as for instance a mechanically actuated electrical switch disposed in the control circuit of the system, which is adapted to cutoff the power to the motor which lifts the elevator in the event that the elevator moves past its normal maximum height. However, such safety devices are not absolutely fail-safe and sometimes do not stop upward movement of the elevator, whereupon the 'elevator will collide with the upper end of the load carrier and at times do extensive damage to the load carrier. If during the collision the lift mechanism for the elevator fails, the elevator tends to fall due to gravity, toward ground level, sometimes causing extensive damage to the warehousing system.

SUMMARY OF THE INVENTION The present invention provides an automatic warehousing system which includes a mechanical latch means adapted for coaction between the elevator and the upper section of the load carrier, for automatically holding the elevator in raised position, in the event that the elevator moves past its normal safe upper travel limit with respect to the conveyor portion of the load carrier. Thereafter, in order to lower the elevator, the latch mechanism has to be de-actuated before the elevator can be moved downwardly with respect to the conveyor portion. The invention also provides cushioning or bumper means for cushioning impact between the elevator and the upper section of the conveyor portion of the load carrier, so as to attempt to prevent damage to the load carrier and destruction of the lift mechanism which raises and lowers the elevator, when the usual safety devices normally provided in the system, fail to operate properly.

Accordingly, an object of the invention is to provide a novel warehousing system.

A further object of the invention is to provide a warehousing system having a powered load carrier for depositing loads into or removing loads from the storage frame or rack in the system, and wherein the load carrier comprises an elongated generally upright conveyor portion and an elevator portion movable vertically relative to the conveyor portion, with power means, such as an electric motor, for moving such elevator portion, and wherein a mechanically actuated latch mechanism is provided adapted for automatic coaction between the elevator and the upper section of the conveyor portion, so as to positively hold the elevator in raised condition in the event that the elevator inadvertently moves beyond its normal upper travel limit.

A still further object of the invention is to provide a warehousing system of the latter mentioned type which includes cushioning means for cushioning impact between the elevator and the upper section of the conveyor portion of the load carrier, in the event that the elevator inadvertently moves into engagement with the upper section of the conveyor portion.

A still further object of the invention is to provide warehousing system of the aforediscussed type wherein the cushioning means is adapted to not only cushion the impact of the elevator with respect to the conveyor portion of the load carrier but also to attempt to cause stalling of an electric motor driving the elevator, and preventing destruction of the connections of flexible lift chains to the elevator and to the motor.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken, generally diagrammatic, fragmentary side elevational view of an automatic warehousing system embodying the invention;

FIG. 2 is a fragmentary, generally diagrammatic, side elevational view of the load carrier illustrating the elevator raised to a position beyond the desired maximum normal travel limit, and illustrating the latch mechanism in operative condition holding the elevator at the upper section of the load carrier;

FIG. 3 is an enlarged end elevational view of the elevator and associated extractor illustrating the latch mechanism on the elevator and conveyor portions of the load carrier, and also illustrating cushioning means on the elevator adapted for resiliently cushioning engagement between the elevator and the upper end of the conveyor portion of the load carrier, the conveyor portion being shown in fragmentary, diagrammatic form;

FIG. 4 is an enlarged, side elevational view of one of the latch bar assemblies of the latch means;

FIG. 5 is an enlarged, side elevational view of one of the catch members of the latch means; I

FIG. 6 is an enlarged end elevational view of the catch member of FIG. 5, taken from the left-hand side thereof;

FIG. 7 is an enlarged, fragmentary illustration of the attachment of the latch bar assembly of FIG. 4 to the upper section of the conveyor portion of the load carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now again to the drawings, the exemplary warehousing system 12 illustrated in FIG. 1 may comprise a storage frame or rack 14 disposed alongside an aisle or travel zone 16, so as to permit a mechanized load carrier indicated generally at 18, to be moved along the aisle or travel zone, and to insert and/or withdraw loads or articles L from the storage bins 19 in the storage frame.

As shown, the storage frame may be constructed of a-plurality of vertically extending posts 22 having a plurality of generally horizontally extending, elongated load supporting members 23 attached thereto, and which provide a plurality of the aforementioned storage bins 19, the latter having open load receiving ends defining. a generally vertical plane. The loads stored in the storage rack are mounted in the individual bins by bridging the loads across laterally opposed of the flanges of the support members 23, as shown in FIG. 1. The loads may be carried upon pallets P (FIG. 1) for handling and/or storing purposes. The instant arrangement of storage frame may be generlaly similar to that disclosed in assignees U. S. Pat. No. 3,402,835 issued Sept. 24, l968 in the name of Sanford Saul.

The load carrier 18 may comprise horizontally movable conveyor portion 24 including vertically elongated mast structure providing tracks 24a connected across the top thereof by an upper end frame section 26, with said mast structure extending upwardly from lower frame section 28 of the conveyor portion, defining a wheeled carriage. The mast structure preferably is disposed along the center line of the aisle 16, with the tracks 24a of such mast structure being spaced apart in the lengthwise direction of the aisle, as shown in FIG. 1. Upper frame 26 may be provided with wheels 30 or the like, for guiding engagement with an over-head track or guide 32 carried by the storage rack 14. The lower frame or carriage 28 may also be provided with wheels or rollers 34 for rolling engagement with base rail 36. At least one of thewheels 34 can be power driven for driving the load carrier horizontally along the aisle. Such driving may be accomplished for instance, by a reversible electric motor and associated geared reduction unit 38.

Movable vertically relative to the mast structure 24a isthe elevator portion 40 of the load carrier. Elevator portion 40 may comprise side portions 42 having vertically spaced sets of flanged rollers or wheels 42a rotatably mounted thereon (FIGS. 2 and 3) adapted for rolling coaction with the respective of the aforementioned tracks 24a of the mast structure, for guiding the vertical movement of the elevator with respect to the conveyor portion of the load carrier. Side portions 42 of the elevator may be connected by transversely extending top, middle and bottom end portions 43 (FIG. 3).

Mounted generally centrally on the elevator may be an extractor portion 44 which is adapted to move laterally of the elevator with a load L supported thereon, for depositing the load in a selected storage bin of the storage rack, or to move laterally of the elevator and pick up a load which is already stored in the associated storage rack and move it back into the elevator, after which the load is adapted to be transferred by the load carrier to a pick-up and discharge station (not shown) associated with the storage rack. The extractor 44 preferably provides an extensible table, with the table being extendible in either direction transverse to the longitudinal direction of movement of the load carrier in the travel zone, so as to locate the extractor to either side of the travel zone. Suitable power means, such as for instance a reversible electric motor 46 may be provided, operatively coupled to the extractor for actuating the latter in its movement relative to the elevator.

The programmed operation of the load handling cycle for the load carrier may be controlled by an electrical control circuit as disclosed for instance in aforementioned U. S. Pat. No. 3,402,835. For example, with the load carrier initially disposed at a beginning point in the system, such as the aforementioned pick-up and discharge station, the load carrier may be automatically moved along the travel zone and located opposite the storage bins of the storage rack. At the selected storage bin during the control interval, the extractor portion 44 may be actuated so that a load may be deposited into or withdrawn from the confronting storage bin. For example, a load may be deposited into the selected bin at a first position and a second load withdrawn from a second bin in the second position, and then conveyed back to the aforementioned pick-up and discharge station, or the load handling cycle may conclude after the load handling at the first position in the system. The load carrier may be programmed from a control panel (e.g., 48) mounted on the load carrier, or it may be programmed from a location remote from the load carrier.

A power unit, such as for instance a reversible electric motor 50 (FIG. 1), may be mounted on the conveyor portion of the load carrier and coupled by suitable speed reduction mechanism 52 to laterally disposed sprockets 54, secured to a common shaft 54a rotatably mounted on the upper frame 26 of the conveyor portion. Each sprocket may coact with a flexible support member, such as for instance a chain 56 which is connected as at 56a to the respective side of the elevator, so that upon actuation of the motor unit 50, the elevator is caused to move vertically relative to the conveyor portion of the load carrier.

As aforementioned, safety means are conventionally provided, such as for instance spring loaded safety switch 57 disposed on the elevator in the path of an actuator lug 57a on the mast structure (FIG. 1) so as to I stop upward movement of the elevator when it rises upwardly to its maximum desired position with respect to the conveyor portion. However, due to failure of such safety devices, sometimes the elevator portion continues upwardly beyond its maximum desired 7 range, whereupon the elevator impacts against the upper end frame 26 of the conveyor portion, and either damages the elevator, or sometimes the drive motor 50 for the elevator continues to'operate, causing failure of the flexible support members 56 and their coupling attachment to the elevator or to the motor. Failure of the lift system may cause the elevator to come crashing down, as actuated by gravity.

In accordance with the present invention, .there is provided latch means 58, adapted for coaction between the elevator portion and the conveyor portion, when the elevator portion has inadvertently moved upwardly beyond the normal safe upper travel limit with respect to the conveyor portion, so as to hold the elevator portion thereat and positively prevent it from moving downwardly relative to the conveyor portion. In the event that the elevator portion inadvertently moves upwardly beyond the maximum desired travel limit of elevation with respect to the conveyor portion, such as might occur in the event of failure of the aforementioned safety device (e.g., 57) which is conventionally provided in the system for limiting maximum height movement of the elevator portion, the elevator portion would run into the upper frame of the conveyor portion. If the electric motor 50 continues to operate after impact, the flexible support chains 56 will either be ripped from their connections to the elevator portion, or the coupling to the motor 50, and substantial damage to the elevator portion and to the upper end of the conveyor portion might occur. If the flexible support chains fail, the elevator portion will tend to fall downwardly due to the action of gravity, toward ground level.

The latch means 58 insures that in the event that the elevator portion moves upwardly beyond the usual safety means for the system, that the latch means will automatically be actuated to positively hold the elevator in its raised position, and the operator is alerted that something is wrong, and a repairman can then ascend the conveyor portion and determine what the problem Some latch means, in the embodiment illustrated, comprises a pair of catch members 60 spaced laterally of the longitudinal center plane of the load carrier, and attached as by means of any suitable fastening means, such as for instance threaded fasteners, to the associated upper cross member 43 on the upper end of the elevator portion, as can be best seen in FIGS. 2 and 3.

Each such catch member 60 comprises a head portion 62 defining a recess 62a therein, thus giving a hook-like configuration (in side elevation-FIG. 5) to the catch member, and a body portion 64 having leg sections 64a. Leg sections 64a may be provided with openings 66 therein for receiving the aforementioned fastening means therethrough. Head portion 62 of the catch member preferably has a cam surface 68 provided thereon for a purpose to be hereinafter set forth. Leg sections 64a straddle the aforementioned upper end cross member 43 of the elevator, and aid in anchoring the catch members 60 to the elevator.

Mounted on one of the side beams 70 of the upper frame 26 of the conveyor portion are a pair of latch bar assemblies 72 (FIGS. 2, 3 and 4). Each latch bar assembly comprises a housing 76 defining a guide-way or passageway 76a in which is mounted latch bar member 78 for movement lengthwise of the housing 76 in the passageway 76a. Latch bar 78 includes a front end portion 78a which preferably has a cam surface 80 provided thereon. Cam surface 80 is adapted for sliding coaction with the aforementioned cam surface 68 on the respective catch member 60 to cause movement of the latch bar from its usual forwardly projecting active position,

to a rearwardly disposed inactive position in the event of movement of the elevator portion beyond its maximum safe travel limit due to failure of the usual safety devices of the warehousing system.

A spring 82 coacts with the latch bar 78 to normally urge it to its active position, and upon pushing engagement of the associated catch member against the cam surface 80 on the latch bar, the latter is moved rearwardly against the resistance to compression of the spring, to permit the passage of the catch member passed the forwardly projecting front end portion 78a of the associated latch bar. Once the head 62 of the catch 60 passes the latch bar, the spring 82 automatically moves the latch bar 78 outwardly of the housing toward active position, wherein portion 78a is received into the recess 62a in the catch, whereupon the elevator portion is positively latched to the conveyor portion and prevented from downward movement relative to the conveyor portion. It will be noted that recess 62a in the catch preferably has a sloping lower surface 84 thereon, which may coact with the cam surface and permit the elevator to still rise upwardly a slight amount after entry of latch bar 78 into the recess 62a of the associated catch. However, the spring 82 actively maintains the coaction between the latch bar and the catch, to insure positive latching of the elevator portion in its raised condition. Latch bar 78 may have a rearwardly projecting stem portion 86 which coacts with the spring in aligning the spring with respect to the latch bar and with respect to the guide passageway 76a in housing 76. Rollers 88 may be provided on the housing 76 for facilitating the movement of the latch bar with respect to the housing and aid in preventing binding of the latch bar in the housing. An actuating knob 90 is preferably attached to the latch bar and projects laterally through a slot 92 in the side of the housing, whereby the latch bar can be manually moved lengthwise of the housing.

In order to cushion the contact between the elevator portion and the conveyor portion upon movement of the elevator portion upwardly beyond its maximum normal elevation with respect to the conveyor portion, there is provided cushioning or bumper mechanism 94 adjacent all four corners of the elevator portion at the upper extremity thereof (FIGS. 1 and 3). Such bumper or cushioning mechanism comprises a mounting plate 96, and a resilient cushioning pad 98 attached thereto. Such pad may be, for instance, a relatively hard rubber pad to absorb the impact between the elevator portion and the conveyor portion upon movement of the elevator portion upwardly toward engagement with the upper section of the conveyor portion, and in the embodiment illustrated upper frame 26 thereof. As can be seen, such rubber pads 98 are adapted to engage the under side of the respective sidebeams 70 of the upper frame, to prevent damage to the elevator in the event of failure of the usual safety devices (e.g., 57) of the system and impact of the elevator with the conveyor portion. Such pads also facilitate the stalling out of the electric motor 50 and thereby aid in preventing the electric motor from tearing the connections of the flexible lift chains to the elevator portion and/or to the motor from their anchoring points. Such a controlled slowing down of the elevator portion due to the pads will aid in causing circuit breakers to trip in the electric circuit and cut-off the electric motor 50 without damage thereto, in the event of engagement between the elevator portion and the upper frame 26 of the conveyor portion. The latch mechanism will retain the elevator portion in its raised position, and alert the ware- 7 housing operator that there has been a failure in the usual safety devices of the system.

From the foregoing discussion and accompanying drawings it will be seen that the invention provides a novel automatic warehousing system including a mechanized load carrier having a vertically movable elevator portion and having mechanical latch mechanism adapted to automatically hold the elevator portion at the upper section of the load carrier, and prevent the elevator portion from moving downwardly toward ground level, in the event that the elevator portion inadvertently moves upwardly beyond the normal maximum range of travel. The invention also provides cushioning means in conjunction with the latch mechanism for aiding in cushioning impact of the elevator with the upper section of the load carrier structure so as to prevent major destruction of the load carrier parts and eliminate long periods of down-time for the warehousing system when failure of the usual electrical safety mechanism in the system occurs.

The terms and expressions which have been used are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of any features shown or described, or portions thereof, and it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. In an automatic storage system comprising a storage rack having means defining a plurality of storage volumes, an aisleway disposed alongside said storage rack and a mechanized load carrier movable in said aisleway for depositing loads into and removing loads from selected storage volumes, said load carrier comprising a vertically elongated longitudinally movable conveyor portion, a vertically movable elevator portion mounted for movement on said conveyor portion, power means for moving said elevator portion vertically relative to said conveyor portion,an extractor portion mounted on said elevator portion and movable into and out of a selected storage volume to transfer a load therebetween, and latch means adapted for coaction between said elevator portion and said conveyor portion for automatic latching in the event said elevator portion inadvertently moves upwardly to a predetermined location on the upper end section of said conveyor portion, to retain said elevator portion thereat.

2. A system in accordance with claim 1 wherein said latch means comprises a latch member on said elevator portion and a latch member on said conveyor portion adapted for automatic interlocking upon predetermined engagement with one another, to prevent movement of said elevator portion downwardly away from said latch member on said conveyor portion.

3. A system in accordance with claim 1- including cushioning means adapted for coaction between said elevator portion and said upper end section of said conveyor portion for cushioning impact therebetween.

4. A system in accordance with claim 1 wherein said conveyor portion of said load carrier includes an upper frame at the uppermost end of said upper end section and a lower frame, and mast structure connecting said frames, said mast structure providing guiding means for the vertical movement of said elevator portion with respect to said conveyor portion of said load carrier, and bumper means on said elevator portion adapted to resiliently cushion engagement between said elevator portion and said upper frame upon inadvertent upward movement of said elevator portion into engagement with said upper frame.

5. A system in accordance with claim 1 wherein said elevator portion includes resilient pads located on said elevator portion and adapted for cushioning abutment with the uppermost end of said upper end section of said conveyor portion, for cushioning the impact of the 6. A system in accordance with claim 3 wherein said power means for moving said elevator portion vertically includes flexible support means movably mounted on said conveyor portion and attached to said elevator portion, said power means including a motor to which said flexible support means is operatively connected whereby energization of said motor causes movement of said flexible support means to cause generally vertical movement of said elevator portion relative to said conveyor portion, and wherein said motor means in use is adapted to stall upon abutting engagement of said cushioning means with the uppermost end of said upper end section of said conveyor portion.

7. A system in accordance with claim 1 wherein said latch means comprises a catch member projecting upwardly from said elevator portion and adapted for automatic holding coaction with a latchbar mounted on the upper end section of said conveyor portion upon movement of said catch member past said latch bar.

8. A system in accordance with claim 7 wherein said catch member includes a head portion and said latch bar is spring loaded and includes cam means thereon for causing automatic retraction of said latch bar with respect to said catch member during movement of said catch member past said latch bar, whereupon said latch bar is then automatically moved into holding coaction with said catch member after vertical passage of said head portion of the catch member past the latch bar.

9. A system in accordance with claim 8 wherein said latch bar includes a mechanical spring providing said spring loading thereof, and means for moving said latch bar against the resistance of said spring for moving said latch bar to inactive position.

10. A system in accordance with claim 4 wherein said elevator portion comprises a framework including ro-' tatable guide means thereon adapted for rotatable guiding coaction with respect to said mast structure, for guiding the movement of said elevator portion vertically relative to said mast structure ofsaid conveyor portion, said latch means comprising a catch member including a hook-like head projecting upwardly above the upper extremity of said elevator portion and a latch bar mounted on the uppermost end of said upper section, and said catch member being so arranged with respect to said latch bar so that said head of said catch member moves upwardly past saidlatchbar prior to engagement of said bumper means with said upper frame of said conveyor portion, whereby said latch bar automatically moves to active position to retain said elevator portion adjacent said uppermost end.

11. A system in accordance with claim 4 wherein said latch means is offset to one side only of the longitudinal vertical center plane of said load carrier.

12. A system in-accordance with claim 9'including guide means for said spring to guide the compression thereof upon movement of said latch bar to inactive position.

13. A system in accordance with claim 7 wherein said catch member comprises a head portion and a body portion said head portion defining a recess into which said latch bar is adapted for automatic movement upon movement of said head portion of said catch member past said latch bar, saidbody portion including leg sections having means thereon attaching said catch member to said elevator portion, said catch member being during lengthwise movement thereof, and means projecting laterally of said latch bar for actuating said latch bar from active to inactive position and vice versa, said latch bar including spring means for automatically urging said latch bar to said active position, and said housing defining a pathway guiding movement of said latch bar with respect thereto during its movement from said active to said inactive position and vice versa. III

Claims

1. In an automatic storage system comprising a storage rack having means defining a plurality of storage volumes, an aisleway disposed alongside said storage rack and a mechanized load carrier movable in said aisleway for depositing loads into and removing loads from selected storage volumes, said load carrier comprising a vertically elongated longitudinally movable conveyor portion, a vertically movable elevator portion mounted for movement on said conveyor portion, power means for moving said elevator portion vertically relative to said conveyor portion, an extractor portion mounted on said elevator portion and movable into and out of a selected storage volume to transfer a load therebetween, and latch means adapted for coaction between said elevator portion and said conveyor portion for automatic latching in the event said elevator portion inadvertently moves upwardly to a predetermined location on the upper end section of said conveyor portion, to retain said elevator portion thereat.

3. A system in accordance with claim 1 including cushioning means adapted for coaction between said elevator portion and said upper end section of said conveyor portion for cushioning impact therebetween.

5. A system in accordance with claim 1 wherein said elevator portion includes resilient pads located on said elevator portion and adapted for cushioning abutment with the uppermost end of said upper end section of said conveyor portion, for cushioning the impact of the elevator portion therewith in the event of its inadvertent engagement with said uppermost end.

6. A system in accordance with claim 3 wherein said power means for moving said elevator portion vertically includes flexible support means movably mounted on said conveyor portion and attached to said elevator portion, said power means including a motor to which said flexible support means is operatively connected whereby energization of said motor causes movement of said flexible support means to cause generally vertical movement of said elevator portion relative to said conveyor portion, and wherein said motor means in use is adapted to stall upon abutting engagement of said cushioning means with the uppermost end of said upper end section of said conveyor portion.

7. A system in accordance with claim 1 wherein said latch means comprises a catch member projecting upwardly from said elevator portion and adapted for automatic holding coaction with a latch bar mounted on the upper end section of said conveyor portion upon movement of said catch member past said latch bar.

10. A system in accordance with claim 4 wherein said elevator portion comprises a framework including rotatable guide means thereon adapted for rotatable guiding coaction with respect to said mast structure, for guiding the movement of said elevator portion vertically relative to said mast structure of said conveyor portion, said latch means comprising a catch member including a hook-like head projecting upwardly above the upper extremity of said elevator portion and a latch bar mounted on the uppermost end of said upper section, and said catch member being so arranged with respect to said latch bar so that said head of said catch member moves upwardly past said latch bar prior to engagement of said bumper means with said upper frame of said conveyor portion, whereby said latch bar automatIcally moves to active position to retain said elevator portion adjacent said uppermost end.

12. A system in accordance with claim 9 including guide means for said spring to guide the compression thereof upon movement of said latch bar to inactive position.

13. A system in accordance with claim 7 wherein said catch member comprises a head portion and a body portion said head portion defining a recess into which said latch bar is adapted for automatic movement upon movement of said head portion of said catch member past said latch bar, said body portion including leg sections having means thereon attaching said catch member to said elevator portion, said catch member being adapted for holding coaction with said latch bar for holding said elevator portion at its uppermost end of travel with respect to said conveyor portion after impacting engagement of said elevator portion with said conveyor portion.

14. A system in accordance with claim 1 wherein said latch means includes a latch bar, means for automatically moving said latch bar lengthwise thereof, a housing containing said latch bar, roller means mounted on said housing for rolling coaction with said latch bar during lengthwise movement thereof, and means projecting laterally of said latch bar for actuating said latch bar from active to inactive position and vice versa, said latch bar including spring means for automatically urging said latch bar to said active position, and said housing defining a pathway guiding movement of said latch bar with respect thereto during its movement from said active to said inactive position and vice versa.