Apparatus for adjusting and controlling the actuation speed of elements belonging to a suspended platform

Abstract

 A apparatus (300) for adjusting and controlling the actuation speeds of elements belonging to suspended platforms. The apparatus (300) comprises a motor (303), a pump (304) mechanically connected to the motor (303), an actuator cylinder (302), and a hydraulic cylinder (301) arranged between the pump (304) and the actuator cylinder (302). Furthermore, hydraulic circuit (301) comprises a slider valve (306). In apparatus (300), the oil flow rate towards the slider valve (306) and towards the actuator cylinder (302) is varied by means of control signals (SC1, SC2) sent to a logic unit (319), which controls the rpm of the variable rpm motor (303). The pumping unit (304) is a fixed displacement unit.

Description

[0001] The present invention relates to an apparatus for adjusting and controlling the actuation speed of elements belonging to suspended platforms.

[0002] For a detailed description of a suspended platform and its operation, the reader is referred to Italian patent applications BO2005A000312 and BO2005A000313 (filed on May 3rd, 2005) by the Applicant. Therefore, the relative parts of the descriptions referred to corresponding figures 1 shall be considered as integral parts of the present description.

[0003] It is known that elevatable working platforms (also called "suspended platforms"), in order to comply with national and European directives, must display features so that the moving elements (e.g. pivoting arms which support the suspended platform) provide peripheral actuation speeds ≤0.4m/s.

[0004] Until now, in suspended platforms of the hydraulic type, the speed of each arm was controlled by limiting the oil flow rate conveyed to each cylinder which actuates the arm itself.

[0005] It is also known that each hydraulic cylinder displays a difference of area between "rod side" and "bottom side" due, indeed, to the presence of the rod on one side. For this reason, the oil flow rate sent either to "rod side" or to "bottom side" must be controlled in order to achieve that the actuating speeds of the arms remain in any case under the specified 0.4m/s.

[0006] Currently, there are different ways of limiting the oil flow rate sent to the hydraulic cylinders, and therefore the actuation speed of the arms; the main two will be described below:

FIRST SOLUTION: the hydraulic distributor controls the flow rate and sends a first part of the oil to the hydraulic actuator cylinder, while the second part of the oil is sent towards the exhaust;

SECOND SOLUTION: according to the movement intended to be carried out, a signal is sent to the pump which varies its displacement as a consequence,; it is apparent that in this case a variable displacement pump is required.

[0007] Figure 1 schematically shows the aforesaid FIRST SOLUTION of an apparatus 100 for adjusting and controlling the actuation speed of elements belonging to suspended platforms.

[0008] In this first solution, belonging to the prior art, 101 is a hydraulic circuit adapted to send pressurised oil to an actuator cylinder 102 related to an arm (not shown) of the suspended platform (not shown).

[0009] Apparatus 100 comprises, in the known way, a thermal engine or electrical motor 103, which turns a fixed displacement pump 104 which takes oil from a reservoir S.

[0010] Pump 104 sends pressurised oil to a hydraulic distributor 105, belonging to the hydraulic circuit 101, adapted to control the mentioned actuator cylinder 102.

[0011] In the embodiment shown in figure 1, a manual hydraulic distributor 105 is shown by way of example only, but either electrical or hydraulic controls (not shown), or several hydraulic distributors (not shown) for controlling all of the actuator cylinders (not shown) of the suspending platform (partially shown) may be provided.

[0012] If the acceleration level of engine 103 is determined beforehand by the operator, pump 104 sends a constant oil flow rate to distributor 105.

[0013] In the known way, actuator cylinder 102 displays a "rod side" 102a and a "bottom side" 102b.

[0014] Furthermore, distributor 105 comprises a valve 106 with three sliders 106a, 106b, 106c subjected to the elastic bias of a spring 107 which allows the return to central position at rest step.

[0015] The pressurised oil is sent to valve 106 from pump 104 by means of a main conduit 108 which, in a point P, branches off into three secondary conduits 109, 110, 111.

[0016] Secondary conduit 109 is provided, in the known way, with a valve element 112 which opens as soon as the oil pressure in the secondary conduit 109 reaches a certain value.

[0017] Furthermore, secondary conduit 110 displays a safety element 113 for limiting the pressure in the hydraulic circuit.

[0018] In the configuration shown in figure 1, the "working position" of valve 106 is occupied by slider 106c in "neutral" position and all of the oil is exhausted towards reservoir S using secondary conduit 111 and an exhaust conduit 114.

[0019] In another configuration (not shown), the "working position" is occupied by slider 106a after the user has imparted, with the known means, an order related to the operation of a mechanical arm coupled to apparatus 100. In this case, the oil crosses secondary conduit 109 (opening valve element 112), passes valve 106 and, along a branch 115, reaches "bottom side" 102b pushing a piston PT of actuator cylinder 102 in a direction identified by an arrow F1. Piston PT is provided with a rod ST.

[0020] Piston PT, shifting according to arrow F1, pushes the oil present on "rod side" 102a which is exhausted through a branch 116, an auxiliary conduit 117 and the exhaust conduit 114 reciprocally arranged in series.

[0021] It must be noted that if the same amount of oil were sent to "rod side" 102a through branch 116 when slider 106b is in "working position" (not shown), since surface SP1 of piston PT on "rod side" 102a is smaller than surface SP2 (due to the presence of rod ST), piston PT would have higher speeds on "bottom side" 102b (with respect to the displacement according to arrow F1) during a displacement according to an arrow F2, opposite to arrow F1. This fact would be detrimental to safety because the maximum speeds allowed could be exceeded.

[0022] Therefore, in order to limit the speed of piston PT when it is shifted along arrow F2, part of the oil in slider 106b is bypassed through an exhaust hole 118 which is aligned with secondary conduit 111 and with exhaust conduit 114.

[0023] Figure 2 schematically shows the aforesaid SECOND SOLUTION of an apparatus 200 (partially shown) for adjusting and controlling the actuation speed of elements belonging to suspended platforms.

[0024] Identical or similar elements which are found in the embodiment of figure 2 (with respect to those present in figure 1) are numbered by adding 100 to the numbering system adopted for the embodiment of figure 1. Therefore, identical elements will not be described again.

[0025] As previously mentioned, the SECOND SOLUTION uses a hydraulic circuit 201 similar to hydraulic circuit 101 of the first embodiment shown in figure 1, to which however significant changes have been made.

[0026] Indeed, a variable displacement pump is used in the SECOND SOLUTION. Furthermore, according to the intended movement (according to F1 or according to F2), signals SG1, SG2 from valve 206 are sent to the pump. Pump 204, therefore, adjusts the oil flow to be sent to hydraulic distributor 205 and therefore to actuator cylinder 202 as a consequence. Another difference between the two solutions is given by the different distributors used. Indeed, the hydraulic distributor 206 in figure 2 does not display any exhaust hole in slider 106b.

[0027] However, both solutions shown in figures 1 and 2 do not ensure optimal safety conditions.

[0028] More in detail, one may say that in the first solution if the operator selects a fixed motor rpm other than nominal rpm, the flow rate sent by pump 104 will be varied. Consequently, also the losses of load through hole 118 will also vary, while the pressure induced in cylinder 102 and therefore in the circuit remain unchanged. A variation of the ratio between the flow rate sent to the cylinder and the flow rate sent to the exhaust and therefore a variation of speed of the cylinder itself ensues.

[0029] The greatest problem related to the second solution is instead constituted by the complexity of the pump used in that application and by the consequent high cost of the pump itself.

[0030] Therefore, it is the object of the present invention to make an apparatus for adjusting and controlling the actuation speed of elements belonging to suspended platforms which is capable of overcoming the drawbacks described above.

[0031] Therefore, the object of the present invention is an apparatus for adjusting and controlling the actuation speed of elements belonging to suspended platforms as shown in claim 1.

[0032] The present invention will now be described with reference to accompanying figure 3 illustrating a non-limitative embodiment example.

[0033] Identical or similar elements which are found in the embodiment of figure 3 with respect to those present in figures 1,2 are numbered by adding 100 to the numbering system adopted for the embodiment of figure 2. Therefore, identical elements will not be described again.

[0034] In figure 3, 300 indicates as a whole an apparatus for adjusting and controlling the actuation speed of elements belonging to suspended platforms according to the present invention.

[0035] In the present invention, as shown in figure 3, the oil flow towards distributor 305 and towards actuator cylinder 302 is varied by means of control signals SC1, SC2 sent from the control system of distributor 305 to logical unit 319, which controls the variable rpm motor 303 coupled to a fixed displacement pump 304.

[0036] In particular, according to the movement to be performed (according to F1 or according to F2) signals SC1, SC2 are sent to logical unit 319, which drives motor 303, imposing the rpm of the motor 303 itself, and therefore, the flow rate that pump 304 sends to distributor 305 and to cylinder 302. Furthermore, control signals SC1, SC2 are generated according to each single movement, and in continuous manner.

[0037] Finally, a feedback signal SRC, which is a function of the actual rpm of an output shaft 320 from the motor 303, is sent to the logical unit 319, in order to be compared to the pre-set rpm and to possibly modify the rpm itself.

Claims

1. An apparatus (300) for adjusting and controlling the actuation speeds of elements belonging to suspended platforms; apparatus (300) comprising a drive unit (303), a pumping unit (304) mechanically connected to said drive unit (303), actuator means (302), and a hydraulic circuit (301) arranged between said pumping unit (304) and said actuator means (302), said hydraulic circuit (301) comprising at least one slider valve (306);
apparatus (300) characterised in that the oil flow rate towards said slider valve (306) and towards said actuator means (302) is varied by means of control signals (SC1, SC2) according to each single movement, and in continuous manner, said control signals (SC1, SC2) being sent to a logical unit (319), which controls the rpm of said variable rpm drive unit (303).

2. An apparatus (300) as claimed in claim 1, characterised in that it also provides a feedback signal (SRC), which is a function of the real rpm of a output shaft (320) from said drive unit (303), said feedback signal (SRC) being sent to said logical unit (319) in order to be compared to the pre-set rpm and to possibly modify the rpm itself.

3. An apparatus (300) as claimed in any of the preceding claims, characterised in that said pumping unit (304) is a fixed displacement unit.

4. A suspended platform characterised in that it comprises at least one apparatus (300) as claimed in claims 1-3.

Drawing