RU2228267C2 - Crank - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: invention relates to plastic metal working and it can be used in hot-forging crank presses with main slider-crank operating mechanism. Proposed crank press has bed frame in form of uprights, crossmember and table, two connecting rods and punch slide, and crankshaft with two crankpins and two support journals. Two support journals are installed in bearings of uprights. Third support journal, namely, central one, is arranged between connecting rods and installed in bearing of crossmember. Said central support journal is made with eccentricity displaced to side opposite to eccentricity of crankpins. Value of eccentricity does not exceed half of clearance in upper part of crossmember bearing when punch slide is in extreme upper position. EFFECT: reduced sag of crankshaft without increasing its vertical rigidity. 2 dwg

Description

The proposal relates to press construction, in particular to hot-stamping crank presses (KGShP) or to any other presses with a main operating crank-slide mechanism.

Known KGShP containing a frame consisting of racks, traverse and table, two connecting rods, a slider and a crank shaft with two crank necks and two supporting necks. The latter are installed in the bearings of the racks (Avenue Tyazhmekhpress CJSC, Voronezh, KGShP KG series).

The disadvantage of these presses, taken by us as an analog, is the elastic deflection of the crank shaft during stamping, which reduces the vertical stiffness of the press, which negatively affects the accuracy of the stamped forgings and requires increased diameters of the support and crank necks.

The specified disadvantage of the analogue is to some extent eliminated in the KGShP with three supporting necks of the crank shaft. The third central support neck is located between the connecting rods and installed in the yoke bearing, and the three support necks are aligned (prospectus from Muller Weingarten, Germany, KGShP of the RK series).

In these presses, taken as a prototype, the use of the third central support of the crank shaft in order to reduce its deflection is not effective enough due to the limited load perceived by the central support.

The specified disadvantage of the analogue and prototype is eliminated in the proposed press, comprising a bed consisting of uprights, a traverse and a table, two connecting rods, a slider and a crank shaft with two crank journals and three support journals, two of which are installed in the bearings of the struts, and the third central one is located between connecting rods and installed in the traverse bearing. The press is characterized in that the central support neck of the crank shaft is made with an eccentricity offset in the opposite direction relative to the eccentricity of the crank journals and not exceeding half the clearance in the upper part of the said yoke bearing at the extreme upper position of the slider.

Due to the distinguishing feature of the proposed press, a reduction in the deflection of the crank shaft is achieved without increasing the vertical stiffness of the latter and the crosshead.

The invention is illustrated in figures 1 and 2.

Figure 1 is a section of the upper part of the press along the axis of the crank shaft at the extreme upper position of the slider.

Figure 2 is a section of the upper part of the press along the axis of the crank shaft with the lowest position of the slider and the absence of technological load.

The press contains a bed consisting of racks 1, a traverse 2 and a table (the latter is not shown in the figures), a crank shaft 3 connected to a rotation drive (not shown in the figures), two connecting rods 4, pivotally connected to two crank necks 5 of the shaft 3, and a slider (not shown in the figures) pivotally connected to the connecting rods 4. The crank shaft 3 contains three support journals, two of which 6 are installed in the sliding bearings 7 of the struts 1, and the third central support neck 8 is in the sliding bearing 9 of the yoke 2.

The Central support neck 8 is made with an eccentricity e ₁ shifted in the opposite direction relative to the eccentricity e _{2 of the} crank necks 5.

Press works as follows. In the initial extreme upper position of the slider (figure 1), the support journals 6 are in contact with the lower sections of the bearings 7 under the influence of the unbalanced gravity of the crank shaft 3. On the upper sections of the bearings 7, a clearance S _{1 is} provided. On the lower and upper sections of the bearing 9 there are gaps S ₂ and S ₃ . When the crank shaft 3 is rotated 180 °, the slider takes its lowest position (Fig. 2).

In the absence of technological load (at idle), the gaps S ₁ in the upper sections of the bearings 7 are maintained. On the lower and upper sections of the bearing 9, gaps S ₄ = S ₂ + 2е ₁ and S ₅ = S ₃ -2е _{1 are formed} due to the eccentricity e ₁ opposite to the eccentricity e ₂ . Since e ₁ ≤ 6.5 S ₃ , the idle rotation of the crank shaft 3 occurs without loading the bearings 7 and 9.

During technological loading of the press, the crank shaft 3 and the crosshead 2 undergo elastic bending, the gaps S ₃ from the upper sections are redistributed to the lower parts of the bearings 7. Due to the presence of eccentricity e ₁ and the gaps S ₁ , a decrease in the deflection of the crank shaft 3 is achieved while maintaining the vertical rigidity of the latter and the crosshead.

The effectiveness of the use of eccentricity e ₁ is estimated by the following formula:

where f _B is the deflection of the crank shaft, P is the technological force, C _B and C _t are the vertical stiffness of the crank shaft and crosshead, respectively.

According to the above formula when R KGSHP MH = 125, _C = C _m = 100 MN / mm, S ₁ = S ₃ = 1.4 mm, e ₁ = 0.5 mm shaft deflection f _B = 0,125 mm in the proposed press , f _in = 1.25 mm for a two-bearing shaft in the analogue and f _in = 0.625 mm for a three-bearing shaft in the prototype. In the proposed press, compared with the prototype, five-fold reduction in the deflection of the crank shaft is achieved.

This offer does not protect the design features of the press, allowing mounting and dismounting of bearings, connecting rods and crank shaft.

Claims (1)

A crank press containing a bed consisting of uprights, a crosshead and a table, two connecting rods, a slider and a crank shaft with two crank necks and three support necks, two of which are installed in the bearings of the racks, and the third one is located between the connecting rods and installed in the traverse bearing characterized in that the Central support neck of the crank shaft is made with an eccentricity offset in the opposite direction relative to the eccentricity of the crank journals and not exceeding half the gap in the upper part of the aforementioned traverse bearing at the highest position of the slider.

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