DE3043732A1 - Tilt control for tailgate hoist - has ground sensing switch and tilt sensing switch connected in alternate layout - Google Patents

Abstract

The ground sensing control is located in the linkage which lifts the platform hoist and operates when the linkage has dropped the platform sufficiently. An attitude sensor on the platform provides a feedback control and both switches are interlocked into a safety circuit which ensures the correct operating sequence at all times, i.e. the platform is not tilted during lifting/lowering. The ground sensing control operates independently of ground contact so that the platform is correctly tilted even when a conventional sensing switch is ineffective due to holes in the ground. The interlocked control ensures that the load cannot slip off due to inadvertent tilting.

Description

"Tail lift"

489 The invention relates to a tail lift for trucks dare, with a height-pivotable by means of a pressure cylinder (lifting cylinder) Articulated lifting arm unit as well as by means of a pressure cylinder (lock cylinder) a horizontal axis, which can be pivoted in height, acts as a flap, loading and access ramp as well as serving as a roughly parallel lifting platform between the loading space and the floor level, wherein a switch is provided, which automatically when the platform is lowered controls the platform inclination to form the access ramp.

Such a tail lift is already described in DE-OS 22 54 107 known. This is on the platform outer wall, which is on the floor when the platform is folded down is located, a switch is attached, which when the platform is lowered and parallel to the floor the circuit of a Electromagnet closes, thereby switching platform aversion. Through this When the switch pin is pushed in, the switch becomes the circuit of an electromagnet closed, which attracts and one between the hydraulic circuit and the one-sided actuated lock cylinders arranged control slide moves in such a way, that the lock cylinder pressure medium chamber with the hydraulic circuit return line tied together and the pressure medium inflow line is blocked so that platform tipping (tilting) due to the effective dead weight of the platform compared to the lifting arm unit is possible - whereby the pressure medium from the lock cylinders flows back to the hydraulic tank.

In this embodiment shown, there is the disadvantage that 1. the Always disliked the platform, i.e. even if the lowered lift arm unit is still no stable position (secure support) due to resting on the ground (or something else) Abutment) can be switched, which is why incorrect switching with a safety risk are possible, and 2. the platform aversion is not switched if in the Area in which the tilt-switching switch should have contact with the ground, a recess / Recess (such as trough, gutter, gutter, drain or the like.) Is present.

he invention is based on the object of a tail lift with improved to create electrically controlled platform inclination, with the relatively simple means, i.e. under the most varied of application conditions exact switching of the platform ramp positions (access ramp position or loading ramp position) achieved and incorrect switching avoided.

According to the invention, this is achieved by adding a to the lifting arm unit Placing the same on the floor the lock cylinder (s) for platform tilting arranged switching switch and the platform a position switch for switching the platform -First position, preferably horizontal position, for Raising and lowering are assigned, these two switches in each case alternately (alternately) switchable circuit are arranged and the one circuit Relay for switching the other circuit to fix the platform position, preferably horizontal position, is assigned over the entire platform stroke.

With a tail lift designed in this way, one is always large Safety working automatic inclination (aversion) of the platform given. Swinging down (leaning) of the platform out of the during height adjustment (especially lowering) position is only taken when the lifting arm unit in a stable position on the floor or another solid (stable supportive) Abutment rests securely. An unintentional turning on the platform aversion during height adjustment (lowering / raising) and at about the height of the loading area in the open position platform is excluded, so that greatest security is guaranteed.

The circuit according to the invention has the effect that after the declining has taken place the platform in the ramp position when the switch is actuated "Lift" always first adjusts itself to an approximately horizontal position (loading ramp position), before the platform lift begins. Keeping the platform level is a circuit fixed until a renewed placement of the lifting arm unit on the floor or the like Activation of the locking function causes. Due to the switching position fixing of the platform's horizontal position is also in the case of intermittent and / or one-sided loads as well as vibration caused by them and / or rocking movement, platform rocking impossible because "bouncing" the Contacts of the position switch assigned to the platform do not result in constant switching (Toggling between panning up and down) leads - rather, it is both in the two end positions of the platform horizontal position as well as the entire stroke (An exact horizontal position is guaranteed between the two end positions.

The horizontal position of the platform also enables work (Loading and unloading by means of a tail lift) when on an incline (slope or the like) standing truck - in the previously known version according to DE-OS 22 54 107 the horizontal position the platform is only given when the truck parking space is horizontal.

Advantageously, the tail lift is also largely functional, if one of the two switches of the ramp level electrical switching device fails; the platform can then still move vertically in the loading dock position as well as be folded up into the transport position, it only has to be on the automatic Platform inclination for taking the ramp position can be dispensed with.

A particularly preferred embodiment exhibits as the platform aversion switching switch assigned to a lifting cylinder and on pressure drop, preferably Pressureless, responsive pressure switch on. As a position switch is a simple, single-chamber mercury switch with two connectable through the mercury mass Ladders preferred. The position switches are preferably in the platform loading ramp position, especially horizontal position, "open" and the tilt-switching switch at tlubarm ground contact "closed".

According to a further feature of the invention, the circuits of the tilt-switching switch and the position switch with an optional power supply to one of the two effecting signal source switches, preferably one connected to the relay connected to the pump motor circuit.

Another idea of the invention provides that the two circuits which cause the automatic platform aversion and platform leveling Switching (ramp position switching device) with a switching device for switching the platform functions "open", "lower", "raise", "close" interact, which has only two command switches, namely "lowering" and "lifting", their Switching impulses from a switching line alternately to one of two receivers, preferably solenoid valves of the hydraulic cylinders (lifting cylinders and locking cylinders), leading switching lines are switchable.

Further features of the invention are to be found in the remaining subclaims remove.

The subject matter of the invention extends not only to the features of the individual claims, but also on their combination.

An exemplary embodiment of the invention is shown in the drawing and is explained in more detail below.

1 shows a schematic side view of a vehicle on a vehicle arranged tail lift whose hinged on a vertically pivotable lifting arm unit Platform is lowered to the floor support of the lift arm unit, with the ramp forming Platform inclination is shown in dash-dotted lines, and FIG. 2 is a schematic Representation of a circuit diagram of an electrical circuit for automatic inclination the platform as well as locking the tamping position swiveled up from an inclined position in their angular position relative to the ground.

A tail lift according to the invention has one on a truck chassis attached fastening unit 2, on which a lifting arm unit 3 can be pivoted in height is articulated, which carries a platform 5 pivotable about a horizontal axis 4.

This flap-like mounted platform 5 is from a pivoted up Transport position, in which it (usually) also has the function of a loading space locking wall takes over, by means of at least one pressure medium cylinder designated as a lock cylinder 8 in a loading dock position, preferably with its wing (running surface) 5a horizontally and lying at about the same height as the floor of the loading space, pivotable.

To move the platform 5 in height between the loading area of the truck and a lower loading level is the lift arm unit 3 with at least one than Lifting cylinder 7 designated Druckmi ttelylinder provided. A particularly simple one Construction is given when the lifting cylinder (s) 7 can be acted upon on one side - The arrangement is such that the pressure space is filled when the platform is lifted and is emptied when lowering the platform.

To at least approximately the same relative position in the angular position in relation to the truck parking level on the entire platform lifting path, the lifting arm unit 3 is designed at least approximately as a parallel guide - in there is preferably an exact parallel guide. In one not shown modified version, the lock cylinder 6 as a component (handlebar) of a Parallel guide linkage provided.

The switching of the locking cylinder (s) 6 and lifting cylinder (s) 7 takes place electrically - preferably via these associated solenoid valves (not shown).

The switches for switching the individual functions are in a switch box 8 and the solenoid valves, hydraulic pump, motor and other switching means and the like are housed in a unit box 9. Between these (pos. 8 and 9) there is preferably only a connection via electrical lines 10, 11, 12 (see Fig. 2).

On the one hand, an automatic lowering of the platform 5 into a ramp position to enable and on the other hand the loading ramp position, especially horizontal position of the supporting and / or running surface 5a, to fix the platform 5, i.e. to an unintentional Lowering to prevent the tail lift with an electrically controlled switching device provided, which is referred to as the ramp position switching device 13.

This ramp position switching device 13 has on the lifting arm unit 3 a when placing the same on the ground the lock cylinder (s) 6 for platform tilting switching switch 14 and a position switch preferably assigned to the platform 5 15 to switch the loading ramp position, preferably in a horizontal position. These two switches 14, 15 are arranged in separate circuits 16, 17, which are alternately interconnected with the power supply and wherein according to the invention the circuit 16 of the platform downward pivoting (for the purpose of the loading ramp forming Inclined position) switching on switch 14 a relay 18 for switching the circuit 17 of the position switch 15 to fix the platform loading ramp position (i.e. their relative angular position, especially horizontal position) over the entire stroke of the Platform 5 is assigned.

The switch 14 causing the platform inclination is preferred formed by a pressure switch, which reacts to a drop in pressure, in particular to depressurization, responds and is connected to the pressure medium space of a lifting cylinder 7, so that after Place the lifting arm unit 3 on a fixed abutment, such as the floor, ramp, threshold Or the like., Due to the pressureless cylinder chamber of the platform-lifting only pressurized single-acting lifting cylinder 7 a switching takes place. The contact bridge (switching bridge) of the switch 14 is closed when the lifting arm unit 3 has contact with the ground, i.e.

is securely supported.

The switch designated as position switch 15 is designed in this way and / or arranged that it switches / controls the horizontal position of the platform. In preferably it is formed by a simple mercury switch, in which single-chamber housing protrude only two line poles through the contact bridge-forming Mercury mass can be connected to close a circuit. With a horizontal platform tread 5a, this position switch 15 is open.

Instead of the preferred mercury switch (not shown) can be a pendulum switch, liquid level switch or the like. as position switch 15 be provided.

To adjust the platform loading ramp position despite the preferred horizontal position To be provided in a different relative position, it is advantageous if the position switch 15 is held adjustable in the angular position. This adjustment can be infinitely variable or be feasible in stages.

For the connection of each with the power line 11 (minus phases) connected, either the pressure switch 14 or the position switch 15 containing Circuits / power lines 16, 17 is particularly simple and extremely advantageous Way, a signal source switch 19 is provided, which can be actuated by a relay 20, in particular, has pivotable, switching bridge, which at one end connects to the electrical line 10 (plus phase) connected electrical line 12 is assigned.

The relay 20 is dependent on the activation of the tail lift power supply, thus coupled with the activation of the hydraulic circuit, supplied with power. In It is particularly simple on the one hand with the electrical line 1L and on the other hand connected to the pump motor (not shown), for example Electric line 21 clamped to the motor relay is provided.

In the electrical line 12, a switching relay 22 is arranged, the on two spaced apart, in particular pivotable, switching bridges 23, 24 acts, each on a with a command transmitter, not shown (Switch "lower" / "raise") connected switching line 25/26 are connected and alternately (alternately) on one of two switching to one not shown Receiver, preferably hydraulic cylinder solenoid valve, for switching the platform working position "Lower" / "Open" or "Raise" / "Close" switching lines 27/28 or 29/30 are switchable (relocatable) - see Fig. 2.

The circuit 16 of the lift arm unit 3 associated, tilt-switching Switch 14 is with the switch receivers for "lowering" and "opening" and the circuit 17 of the position switch 15 associated with the platform 5 is connected to the switch receivers for "lifting" and "closing" switchable.

In the particularly preferred embodiment, the connection is between the control box not shown in detail, numbered 8, and the control box not shown in detail shown, numbered with 9 aggregate box to a minimum, namely only three Electrical lines 10-12, limited, which makes a particularly simple and fast feasible switch box assembly when attaching the tail lift to a truck. Even if the connection between the switch box is damaged and Ag (regate box, repair is possible ozone great special knowledge, ropes yes there are only three lines. These three electrical lines can be continuous provided or separable (and e.g.

be coupled in a plug connection) - the number 31 indicates one advantageous separation option.

The electrically controlled automatic inclination (aversion to Access ramp formation) for tail lifts with lifting and locking cylinder (s) works as follows: If the commanding switch "lower" of switch box 8 is actuated, the platform 5 moves to the lowest position, i.e. until it is supported the lifting arm unit 3 on the floor or the like .. If the switch "lowering" is also after the floor support of the lifting arms left actuated, so it comes to a tilt of the Platform 5 until a ramp, i.e. the ramp, has been created. This tilting movement (Inclined position) is via the switch 14, preferably a pressure switch on a Lifting cylinder, initiated, which is then "closed". With lift arm floor support the changeover relay is activated by the switch 14 via the normally closed contact of the relay 20 22 actuated, which the necessary solenoid valves for opening or tilting the platform 5 controls.

The relay 20 is not activated and serves as a signal source switch. When "lowering" the relay is on switch 14 and when "lifting" when the pump motor of the hydraulic circuit is running, it is switched to position switch 15. Is the Platform down and inclined (i.e. in ramp position) and becomes the switch "Lift" operated on the switch box 8, the platform 5 is always in a horizontal position before the lifting process begins. The position switch 15 of the Platform 5 is closed and there when the platform 5 is inclined (inclined) the switch 14 is also closed when the lifting arm unit 3 is supported on the floor is, the relay 18 is actuated and the switching relay 22 can via the uncontrolled Relay 20 can be controlled via the position switch 15 - this means that the platform 5 only begins to lift when it is horizontal (i.e. in Loading ramp position). When the platform has reached the horizontal position, it opens the position switch 15, the lifting begins, and the switch 14 also opens -thereby the position of the platform is fixed in its angular position and also with one Bouncing of the contacts of the position switch 15 results in constant switching and platform rocking avoided because the relay 18 has dropped out via the switch 14 and the ground contact, which is required for switching the changeover relay 22, interrupts. That means, that the platform inclination is only in function when the lifting arm unit 3 rests on a fixed abutment. If one of the two switches 14 or 15 fails, so the platform is generally still usable, it only has to be on the automatic inclination can be dispensed with.

Instead of the single electrical line 12, switch between the functions of the switch box and the two circuits 16, 17 of the ramp position switching device 13, two electrical lines can also be provided, in which case the signal source switch 19 is omitted and each circuit 16, 17 is direct, but always only one of the two, is switchable. The switch is also in this embodiment (not shown) 14 with the command receivers (solenoid valves) for "opening" and "lowering" the platform 5 and the position switch 15 coupled with those for "closing" and "lifting".

Although the from Fig. 2 removable electric switch of the four functions "Open", "Lower", "Raise" and "Close" the platform 5 using only two command transmitters, namely a switch "lower" and a switch "level" extremely advantageous (in particular inexpensive) and therefore preferred, can of course even four, d. H. a separate commanding switch is provided for each function be.

Of course, those from the right part of FIG. 2 removable version of the electric hydraulic cylinder circuit, in which only two command transmitters (switches: "lower" and "lift") and four command receiver switching lines (for "lowering", "opening", "lifting" and "closing") are available, even for tail lifts without the ramp position switching device previously described as essential to the invention be used.

Claims (15)

Claims tail lift for trucks, with one on one articulated lifting arm unit that can be swiveled in height by means of a pressure cylinder (lifting cylinder) and height-pivotable about a horizontal axis by means of a pressure cylinder (lock cylinder) Platform that can be used as a flap, loading and access ramp as well as between loading space and Floor level approximately parallel-guided lifting platform is used, with a switch provided which automatically sets the platform inclination to form when the platform is lowered the access ramp controls, characterized in that a when placing the same on the floor the lock cylinder (s) (6) for platform tilting switching switch (14) and the platform (5) a position switch (15) for switching the platform position of use, preferably horizontal position, for lifting and sinks are assigned, these two switches (14, 15) each in one alternately (alternately) switchable circuit (16, 17) are arranged and the a circuit (16) a relay (18) for switching the other circuit (17) for the purpose of fixing the platform position, preferably horizontal position, on the entire platform stroke assigned. 2. Loading platform according to claim 1, characterized in that the the Platform reluctance switching on switch (14) assigned to a lifting cylinder (7) and is formed by a pressure switch responsive to a pressure drop. 3. Loading tailgate according to claim 1 and / or 2, characterized in that that the switch (14) on the pressure medium chamber, which switches on the platform aversion a hydraulic cylinder (lifting cylinder) (7) that can be acted upon on one side is. 4. Loading platform according to claim 1, characterized in that the position switch (15) from a simple, single-chamber mercury switch known per se two conductors connectable by the mercury mass (drops) is formed. 5. Loading platform according to claim 1, characterized in that the position switch (15) is formed by a pendulum switch. 6. Loading platform according to claim 1, characterized in that the position switch (15) is formed by a liquid level switch. 7. Loading platform in particular according to claim 1, characterized in that that the position switch (15) for changing the platform position with respect to the ground level in its angular position relative to the ramp-forming platform usable surface (5a) is adjustable. 8. tail lift in particular according to claim 1, characterized in that that the circuit (16) of the lifting arm unit (3) associated, inclination-switching Switch (14) with the command receivers, such as solenoid valves, switches for opening " and "lowering" and the circuit (17) of the position switch associated with the platform (5) (15) can be interconnected (interacts) with those for "closing" and "lloben". 9. Loading platform according to claim I and X or 8, characterized in that that the two switches (14, 15) are arranged in such a way that the position switch (15) in the platform loading ramp position, in particular the horizontal position, "open" and the tilt-switching switch (14) is "closed" when the lift arm comes into contact with the floor. 10. Loading platform according to claim 1 and / or 9, characterized in that that the circuits (17, 16) of the position switch (15) and the tilt-switching Switch (14) with an optional power supply to one of the two (16 or 17) causing signal source switch (19) are connected. 11. Loading platform according to claim 10, characterized in that the Signal source switch (19) assigned to the circuit (21) of the hydraulic pump motor Has relay (20). 12. Loading platform according to one or more of claims 1 to 10, characterized in that the electrical switching device for the automatic Inclination and fixing of the horizontal position of the platform (5) to one Assembly (ramp position switching device) (13) is summarized, which is preferably is assigned to an aggregate box (9). 13. Loading platform according to claim 11, characterized in that the Ramp position switching device (13) via electrical lines (10,11,12) with all Switch for switching the individual functions "Open", "Lower", "Lift" and "Close" containing control box (8) are connected. 14. Loading platform in particular according to claim 1, characterized in that that the two circuits (16, 17) of the automatic platform dislike as well Shift causing platform horizontal position (ramp position switching device) (13) with a switching device for switching the platform functions "open", "Lower", "Lift", "Close" interacts, the only two command switches, namely "lowering" and "lifting", whose switching pulses each come from a switching line (25/26) alternately to one of two receivers, preferably solenoid valves, leading switching lines (27) (for "lowering") or (28) (for "opening") or (29) (for "lifting") or (30) (for "closing") are switchable. 15. Tail lift according to one or more of claims 1 to 14, characterized in that the signal source switch (19) of the ramp position switching device (13) via an electric line (12) to a switchover relay belonging to the switch box (8j) (22) is connected, which acts on two contact bridges (23 and 24), each a switching line (25/26) of a "lowering" or "lowering" switch that gives the switching command "Lift" assigned and alternately to the one receiving an impulse Switching element, such as a solenoid valve or the like., Leading switching line "lowering" (27) or "Open" (28) or "Lift" (29) or "Close" (30) are switchable (foldable).