圆锯机安全技术和人机工程方面的研究

引言 圆锯是重要的木材加工机械,在家具生产中广泛应用。其构造如图一所示。机架上 即使是如此简单的机器,也存在着安全技术和人机工程方面的问题。这一项研究工作由不伦瑞克工业大学所属的机床与生产技术研究所进行,得到德国研究团体的赞助。这方面的缺陷会导致操作的不安全,并增大操作者的负担,降低了人—机系统的工作效率。     

双工位横截圆锯木工机床结构设计

针对我国林业生物质发展潜力大,林用专业实用木工机床少,工作效率低等设计背景,提出了一种双工位横截圆锯木工机床的结构设计。介绍了该机床的工作原理、传动结构以及进料拨料机构,用有限元分析软件NX_Nastran对悬臂主轴进行了强度校核分析,以证实在结构上满足设计要求。该木工圆锯机具有双工位、半自动操作的结构特点,专门利用林间枝丫加工成便于燃烧的生物质燃料。     

木工机床与刀具行业标准目录(一)

1.GB/T12488一1990木工机床型号编制方法2.GB/T14383一1993木工机床通用技术条件3.JB/T4171一1999木工机床精度检验通则4.GB12557一2000木工机床安全通则5.GB/T15379一1994木工机床基本术语6.CB/份370一1983木工机床噪声功率级的测定7.JB/释953一1999木工机床噪声声(压)级测量方法8,CB/T10961一1989木工机床操作指示形象化符号9.GB5226.1一2002木工机床机械电气设备第工部分:通用技术条件10.GB/T15378一1994木工机床术语木工锯机11.GB/悦%6一1993纵剖木工圆锯机参数12.GB/T14387一1993纵剖木工圆锯机精度13.JB/竹295一1993单…     

木材加工机床多发性工伤事故的原因及预防

以三类较易发生工伤事故的木材加工机床(圆锯床、平刨床和铣床)为例,分析了导致木材加工机械工伤事故的主要原因,提出了从人和机床两方面预防工伤事故的措施.     

现代木工圆锯机

圆锯机是主要制材锯机之一。近二十年来圆锯机的结构和工作原理都发生了明显变化,如减小锯片厚度,降低了木材损失;完善定位方法,提高了锯割精度;改善锯片结构,简化了修锯作业;采用自动控制,提高了生产效率等等。因此圆锯机生产线在许多情况下都显示出优于其他锯机的技术经济特性。     

木工圓鋸的降声技术

一、木工圆锯机的噪声及其危害木工圆锯机是一种应用非常广泛的木材加工机床。各种不同类型圆锯机的一个共同特点是噪声响度大、频率高、声音刺耳难听。是长期以来未能控制和解决的问题。根据实测证明:各种木工圆锯的声压级     

工具车间的磨床

目前,工具车间所用的磨床普遍是小型、精密而且又是万能的。对现代机床来说,硬质合金圆锯磨削是一种比较简单的操作方法。手工操作的方式在经济上是适宜的。根据它们的机床能力证实了一星期恰好能磨削三片圆锯。此机床易于配上附件使之更万能,能加工其它工具如镂铣刀具,创刀片和整体成形刀头。     

Rockwell新型紧凑电圆锯

Rockwell推出一款新型的Φ114 mm紧凑型电圆锯。这款机型将紧凑型产品的便捷、轻便和多功能结合在一起,收到市场及操作者青睐。到底怎么样?让我们先来看一下这款产品的规格参数。该款紧凑型圆锯配装的锯片为Φ114 mm,在外形尺寸上与同类产品相比更薄,整机重量降低50%左右。对于可以提供5A动力的电机而言,更轻、更薄的锯片意味着它可以在速度     

降低冲压噪音方法浅析

本文研究的主要目的是为了减低冲床的冲裁噪音,以减轻噪音对机床操作者身体健康的危害。经过大量研究我们总结出一条规律,冲裁噪音与冲裁力是成正比例关系变化的,在研究冲击现象时科学家发现,冲击力的大小和冲击力作用时间成反比例。即冲击力作用时间增加,冲裁力减小。主要通过改变模具结构来降低冲床冲裁力和延长冲床冲裁力的作用时间,即采用斜刃口、阶梯凸模,还有加热冲裁法等,从而降低了冲压噪音,改善了工人工作环境,保证了操作者的身体健康。     

美国木工倾斜圆锯机简介

随着我国的对外开放,与一些工业发达国家接触机会增加、技术上的不断往来,对于研究木工机床的技术水平、以及取得借鉴分析都有了一定的进展。最近有机会接触一些国外关于木工倾斜圆锯机资料和设备愿与大家进行交流。     

Nitrogen and phosphorus retention and excretion in late-gestation dairy heifers

The objectives of this study were to evaluate the effects of limit feeding diets containing concentrates or by-products in place of forages on manure and nutrient excretion in growing, gravid heifers. Eighteen Holstein heifers confirmed pregnant were grouped by due date and fed 1 of 3 diets (n = 6 per treatment) for the last 14 wk of pregnancy. Diets were high forage, fed ad libitum (HF); by-product based (BP), fed at the same rate as HF-fed heifers; or low forage (LF), fed at 86% of the HF diet. Diets were designed to supply equal quantities of P, N, and metabolizable energy. Total collection of feces and urine was conducted in wk 14, 10, 6, and 2 prepartum. The HF ration was 90.7% forage, 13.7% crude protein (CP), and contained orchardgrass hay, corn silage, corn grain, soybean meal 44%, and a vitamin-mineral premix. The BP diet was 46.2% forage and 14.0% CP, with 70% of the grain mix space replaced with soybean hulls and cottonseed hulls in a 1:1 ratio, with intake limited to 93% of the dry matter intake (DMI) of HF. The LF ration was 45.3% forage and 17.8% CP, with intake limited to 86% of the DMI of HF. The effect of diet was analyzed with repeated measures, using preplanned contrasts to compare HF with BP and LF with HF and BP. As designed, heifers fed HF and BP had greater DMI than the heifers limit-fed LF, and there was no effect of diet on average daily gain or BW. Intake and digestibility of N were lower, and fecal N excretion was higher, in heifers fed HF and BP than heifers fed LF. Mean feces excretion on both a wet and dry basis was greater for HF heifers compared with BP heifers and less for LF heifers than for HF and BP heifers. Despite differences in urinary output, diet had no effect on urea N excretion, but there was a trend for heifers fed HF and BP rations to excrete less urinary N compared with those fed LF. Compared with HF and BP heifers, LF heifers tended to have lower fecal P excretion and had higher urinary P excretion. Measured manure and urine excretion from heifers fed LF was greater than current American Society of Agricultural and Biological Engineers values, whereas heifers fed HF excreted less manure and urine than predicted. Heifers achieving similar rates of gain from diets differing in forage, grain, and by-product content excreted widely varying quantities of manure.     

Sire contribution to fertilization failure and early embryo survival in cattle

Despite passing routine laboratory tests of semen quality, bulls used in artificial insemination (AI) exhibit a significant range in field fertility. The objective of this study was to determine whether subfertility in AI bulls is due to issues of sperm transport to the site of fertilization, fertilization failure, or failure of early embryo or conceptus development. In experiment 1, Holstein-Friesian bulls (3 high fertility, HF, and 3 low fertility, LF) were selected from the national population of AI bulls based on adjusted fertility scores from a minimum of 500 inseminations (HF: +4.37% and LF: ?12.7%; mean = 0%). Superovulated beef heifers were blocked based on estimated number of follicles at the time of AI and inseminated with semen from HF or LF bulls (n = 3–4 heifers per bull; total 19 heifers). Following slaughter 7 d later, the number of corpora lutea was counted and the uteri were flushed. Recovered structures (oocytes/embryos) were classified according to developmental stage and stained with 4′,6-diamidino-2-phenylindole to assess number of cells and accessory sperm. Overall recovery rate (total structures recovered/total corpora lutea) was 52.6% and was not different between groups. Mean (± standard error of the mean) number of embryos recovered per recipient was 8.7 ± 5.2 and 9.4 ± 5.5 for HF and LF, respectively. Overall fertilization rate of recovered structures was not different between groups. However, more embryos were at advanced stages of development (all blastocyst stages combined), reflected in a greater mean embryo cell number on d 7 for HF versus LF bulls. Number of accessory sperm was greater for embryos derived from HF than for LF bulls. The aim of experiment 2 was to evaluate the effect of sire fertility on survival of bovine embryos to d 15. Day 7 blastocysts were produced in vitro using semen from the same HF (n = 3) and LF (n = 3) bulls and transferred in groups of 5–10 to synchronized heifers (n = 7 heifers per bull; total 42 heifers). Conceptus recovery rate on d 15 was higher in HF (59.4%,) versus LF (45.0%). Mean length of recovered conceptuses for HF bulls was not affected by fertility status. In conclusion, while differences in field fertility among AI sires used in this study were not reflected in fertilization rate, differences in embryo quality were apparent as early as d 7. These differences likely contributed to the higher proportion of conceptuses surviving to d 15 in HF bulls.     

North American techniques for circular saw tensioning and leveling: Practical adjustment methods

This paper describes typical processes used in North America for tensioning and leveling circular saws. It concentrates on the methods used to adjust the tensioning and leveling state of a circular saw, to achieve optimal operating conditions. The paper gives practical details of the adjustment processes involved and explains the theory of how they work.     

Effects of supplementing condensed tannin extract on intake, digestion, ruminal fermentation, and milk production of lactating dairy cows

A lactation experiment was conducted to determine the influence of quebracho condensed tannin extract (CTE) on ruminal fermentation and lactational performance of dairy cows. The cows were fed a high forage (HF) or a low forage (LF) diet with a forage-to-concentrate ratio of 59:41 or 41:59 on a dry matter (DM) basis, respectively. Eight multiparous lactating Holstein cows (62 ± 8.8 d in milk) were used. The design of the experiment was a double 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments, and each period lasted 21 d (14 d of treatment adaptation and 7 d of data collection and sampling). Four dietary treatments were tested: HF without CTE, HF with CTE (HF+CTE), LF without CTE, and LF with CTE (LF+CTE). Commercial quebracho CTE was added to the HF+CTE and the LF+CTE at a rate of 3% of dietary DM. Intake of DM averaged 26.7 kg/d across treatments, and supplementing CTE decreased intakes of DM and nutrients regardless of forage level. Digestibilities of DM and nutrients were not affected by CTE supplementation. Milk yield averaged 35.3 kg/d across treatments, and yields of milk and milk component were not influenced by CTE supplementation. Negative effects of CTE supplementation on feed intake resulted in increased feed efficiency (milk yield/DM intake). Although concentration of milk urea N (MUN) decreased by supplementing CTE in the diets, efficiency of N use for milk N was not affected by CTE supplementation. Feeding the LF diet decreased ruminal pH (mean of 6.47 and 6.33 in HF and LF, respectively). However, supplementation of CTE in the diets did not influence ruminal pH. Supplementing CTE decreased total volatile fatty acid concentration regardless of level of forage. With CTE supplementation, molar proportions of acetate, propionate, and butyrate increased in the HF diet, but not in the LF diet, resulting in interactions between forage level and CTE supplementation. Concentration of ammonia-N tended to decrease with supplementation of CTE. The most remarkable finding in this study was that cows fed CTE-supplemented diets had decreased ruminal ammonia-N and MUN concentrations, indicating that less ruminal N was lost as ammonia because of decreased degradation of crude protein by rumen microorganisms in response to CTE supplementation. Therefore, supplementation of CTE in lactation dairy diets may change the route of N excretion, having less excretion into urine but more into feces, as it had no effect on N utilization efficiency for milk production.     

Marie Ménard apples with high polyphenol content and a low‐fat diet reduce 1,2‐dimethylhydrazine‐induced colon carcinogenesis in rats: Effects on inflammation and apoptosis

Inflammation may increase cancer risk, therefore, we studied whether polyphenol‐rich Marie Ménard (MM) apples with reported anti‐inflammatory activity prevent 1,2‐dimethylhydrazine (DMH)‐induced colon carcinogenesis in rats and, likewise whether high‐fat (HF) diet promoting carcinogenesis, may affect inflammation. DMH‐induced rats were fed for 15 weeks with: an HF diet (23% corn oil w/w); an HF diet containing 7.6% w/w lyophilized MM (apple diet (AD)); a low‐fat (LF) diet and an HF diet containing piroxicam (PXC) (0.01% w/w) as control. Mucin depleted foci (MDF), precancerous lesions in the colon, were dramatically reduced in the AD, LF, and PXC groups compared with the HF. Peritoneal macrophage activation, an index of systemic inflammation, was significantly decreased in the AD, LF, and PXC groups. TNF‐α, iNOS, IL‐1β, IL‐6 m‐RNA expression in the colon, as well as CD68 cells and plasmatic PGE2 were lower in the AD, but not in the LF group. Apoptosis in the MDF of both the AD and LF‐fed rats was significantly higher than in HF rats. In conclusion, AD has a strong chemopreventive effect, reducing inflammation, and increasing apoptosis, while the chemopreventive effect of the LF diet seems mediated mainly by increased apoptosis in MDF.     

Interaction between milk allowance and fat content of the starter feed on performance of Holstein calves

Sixty-six Holstein male calves [42 ± 6.0 kg of body weight (BW) and 12 ± 3.1 d of age] were housed individually and allocated to 1 of 4 treatments following a 2 × 2 factorial complete randomized design to assess the potential interaction between milk replacer (MR) allowance and fat content in the starter feed. Thus, 4 treatments were evaluated: a low-fat (4.1% fat; LF) starter feed offered along with 4 L/d of MR (4LF), a high-fat (11.2% fat; HF) starter feed plus 4 L/d of MR (4HF), a LF starter feed offered with 6 L/d of MR (6LF), and an HF starter feed offered with 6 L/d of MR (6HF). Calves were fed either 4 or 6 L/d of MR (25% crude protein and 19.2% fat) in 2 offers (0800 and 1630 h) and had ad libitum access to either an LF or an HF starter feed (21.4 and 22.3% crude protein). Calves were weaned at wk 6 of study by halving the daily MR allowance for 1 wk. Individual MR and starter feed intakes were recorded daily and BW was determined weekly. A glucose tolerance test was performed on d 30 of study to evaluate the effects of increased energy provision on glucose metabolism. Apparent feed digestibility was measured for the last 5 d of study. Overall, fat content of starter feed had no effect on solid feed intake. However, during wk 8 of study (after weaning), calves in the LF treatment had greater starter feed intake than HF calves. Calves on 6 L/d of MR had greater BW than calves fed 4 L/d from the second week of study until weaning. After weaning, 6LF calves had lesser BW than 6HF calves. Calves on 6 L/d of MR had greater average daily gain than calves fed 4 L/d, and 6HF calves tended to have the greatest average daily gain. Glucose clearance rate tended to be lesser for HF than for LF calves. In conclusion, offering 6 L/d of MR increased growth performance before weaning and, when offering 6 L/d of MR, feeding a high-fat starter feed resulted in the greatest BW after weaning.     

Effect of pork lard content on the chemical, microbiological and sensory properties of a typical fermented meat product (Pitina) obtained from Alpagota sheep

The aim was to investigate the physicochemical, microbiological and sensory properties of Pitina, a typical fermented meat product and evaluate the effect of two levels of pork lard content (Low Fat, LF, 10% vs. High Fat, HF, 30%) on its attributes. HF attained lower pH than LF Pitina, which reached lower water activity. LAB comprised the major flora with substantial counts of micrococci, enterococci and mould and yeast. Gram negative Enterobacteria were recovered as coliforms and faecal coliforms. Listeria monocytogenes was also isolated. The lard level influenced the count of micrococci and some sensory attributes. LF attained higher scores for both hardness and cohesiveness and differed from HF in having a more marked odour of ewe and smoke and sweeter taste. HF had a more pronounced odour and taste of garlic and mould than LF.     

Body composition and hormonal effects following exposure to mycotoxin deoxynivalenol in the high-fat diet-induced obese mouse

Scope: To characterize the effects of ingesting the common foodborne mycotoxin deoxynivalenol (DON) on body weight and composition in the high‐fat (HF) diet‐induced obese mice, a model of human obesity. Methods and results: Female B6C3F1 mice were initially fed HF diets containing 45% kcal (HF45) or 60% kcal (HF60) as fat for 94 days to induce obesity. Half of each group was either continued on unamended HF diets or fed HF diets containing 10 mg/kg DON (DON‐HF45 or DON‐HF60) for another 54 days. Additional control mice were fed a low‐fat (LF) diet containing 10% kcal as fat for the entire 148‐day period. DON induced rapid decreases in body weights and fat mass, which stabilized to those of the LF control within 11 days. These effects corresponded closely to a robust transient decrease in food consumption. While lean body mass did not decline in DON‐fed groups, further increases were suppressed. DON exposure reduced plasma insulin, leptin, insulin‐like growth factor 1, and insulin‐like growth factor acid labile subunit as well as increased hypothalamic mRNA level of the orexigenic agouti‐related protein. Conclusion: DON‐mediated effects on body weight, fat mass, food intake, and hormonal levels in obese mice were consistent with a state of chronic energy restriction.     

Influence of woodworking machine cutting parameters on the surrounding air dustiness

From epidemiological studies experts conclude that wood workers are subjected to an increased health risk of nose and nasal cavity cancer under the influence of oak- and beech-wood dust. That is why, pursuant to Croatian regulations, the limit mass concentration for oak- and beech-wood respirable dust is 1 mg/m³ and for total dust 3 mg/m³. In this study the dustiness of the air surrounding woodworking machines has been researched in two woodworking companies, furniture factory and carpentry. Sampling of respirable and total wood dust from the surrounding air was carried out during workday by the method of personal samplers fixed on workers suit and then the daily dose of workers exposure was determined. Measured mass concentrations exceeded the Croatian limit values: in the furniture factory 16% of samples for respirable dust and 18% for total dust and in the carpentry 38% for respirable dust and 65% of all samples for total dust. In the furniture factory, mass concentration of respirable particles was higher near the belt sander than near the circular saws. At the workplaces of these woodworking machines higher mass concentration of respirable and total wood dust was measured than in the air around other machines, such as spindle moulder, band saw and jointer. In the carpentry mass concentration of respirable particles near the circular saws was significantly higher than near the jointer or lamello router. The highest share of respirable particles in total wood dust are recorded at the workplaces with low concentration of total wood dust and around machines with cutting parameters achieve the lowest value of chip thickness.     

Nutrient demand affects ruminal digestion responses to a change in dietary forage concentration

Previous research in our laboratory has indicated that the physical filling effects of high-forage diets become increasingly dominant in determining feed intake and milk production as nutrient demand increases. This effect was tested further by using 14 ruminally and duodenally cannulated Holstein cows in a crossover design experiment with a 14-d preliminary period and two 15-d experimental periods. During the preliminary period, 3.5% fat-corrected milk yield was 15 to 60 kg/d (mean = 40 kg/d), and preliminary voluntary dry matter intake (pVDMI) was 20.6 to 30.5 kg/d (mean = 25.0 kg/ d). Treatments were a low-forage diet (LF), containing 20% (dry matter basis) forage neutral detergent fiber (NDF), and a high-forage diet (HF), containing 27% forage NDF. The ability of linear and quadratic factors of pVDMI to predict the difference in responses of individual cows to treatments (Y_LF - Y_HF) was tested by ANOVA, with treatment sequence as a covariate. In contrast to results of previous research, differences in dry matter intake and fat-corrected milk yield responses to LF and HF did not depend on pVDMI. This might be because of the combined physical fill and metabolic satiety effects of LF, especially in cows with the greatest pVDMI. Digestion or passage of NDF might have been inhibited on LF among high-pVDMI cows. As pVDMI increased, NDF turnover time increased more on LF than on HF. Among high-pVDMI cows, the NDF turnover time was unexpectedly greater on LF than on HF. With increasing pVDMI, the digestion rate of potentially digestible NDF decreased at a similar rate on both diets. Passage rates of potentially digestible NDF and indigestible NDF were not related to pVDMI, regardless of treatment. Greater starch fermentation (resulting from greater starch intake) for LF as pVDMI increased likely inhibited NDF digestion through pH-dependent and pH-independent effects. Inhibition of NDF digestion might cause LF and HF to have similar effects on dry matter intake, depending on the nutrient demand of individual cows.