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  Hydraulic pump, hydraulic pump unit, and hydraulic driving unitUSPTO Application #: 20070243081Title: Hydraulic pump, hydraulic pump unit, and hydraulic driving unit Abstract: A hydraulic pump can prevent breakage at a high pressure without providing a separate relief valve. A housing has a body side and a lid side that are divided by a surface perpendicular to a rotational axis of a hydraulic pump shaft. The lid-side housing is brought into oil-tight contact with the body-side housing by a spring. Contact between the body-side housing and the lid-side housing is maintained at a predetermined pressure corresponding to a maximum allowable pump hydraulic pressure. (end of abstract)
Agent: Michael L. Crapenhoft - Gifu-city, JP Inventors: Osamu SATO, Yoshitake SAKAI USPTO Applicaton #: 20070243081 - Class: 417310000 (USPTO) Related Patent Categories: Pumps, With Condition Responsive Pumped Fluid Control, Pressure Responsive Relief Or Bypass Valve, Rotary Expansible Chamber Pump The Patent Description & Claims data below is from USPTO Patent Application 20070243081. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The invention relates generally to hydraulic pumping equipment in which a hydraulic fluid is pumped in a hydraulic circuit and used as a source of motive force to drive a hydraulic actuator. The invention relates more specifically to a hydraulic pump used in a hydraulic pump unit in which at least a hydraulic pump and a hydraulic oil tank are integrated. A housing for the hydraulic pump is contained inside the hydraulic oil tank. Embodiments of the invention may also include a hydraulic pump unit provided with a hydraulic pump according to the invention, and a hydraulic driving unit provided with such a hydraulic pump and configured to apply a driving force by hydraulic pressure to a driven body. [0002] Hydraulic pump units in which the hydraulic pump and the hydraulic oil tank are integrated include those in which the hydraulic pump housing is contained in the hydraulic oil tank. [0003] Hydraulic driving units may also include an electric motor for driving the hydraulic pump, a hydraulic actuator that is driven by hydraulic oil from the hydraulic pump, and various valves for controlling the flow of the hydraulic oil between these hydraulic devices. The elements operate together to apply a driving force generated by hydraulic pressure to the driven body. [0004] A hydraulic driving unit of this general type is described in Japanese Laid-Open Unexamined Patent Application Publication No. 02-296000. FIG. 5(a) is a hydraulic circuit diagram for such a hydraulic driving unit; FIG. 5(b) is a view of the unit in partial section; FIG. 5(c) is a front view of a hydraulic pump; and FIG. 5(d) is a section view showing internal structures of the pump illustrated in FIG. 5(c). [0005] Although FIGS. 5(c) and 5(d) are not included in the Japanese publication, they do illustrate the structures of the embodiment described in that document. The applicant in the Japanese publication is the same as the assignee of the invention described in this application. [0006] FIG. 5(a) illustrates a hydraulic driving unit OU operable to impart a driving force to a driven body W through hydraulic pressure delivered by hydraulic oil circulating in a closed system. The hydraulic driving unit includes a hydraulic pump P for pumping hydraulic oil in both normal and reverse directions. The pump is driven by a normal/reverse rotating motor M. A hydraulic actuator C (a hydraulic cylinder, in this case) is driven by pressure in the hydraulic oil to generate the driving force. A hydraulic oil tank T stores a quantity of the hydraulic oil inside a closed volume. A pair of operate check valves OT1 and OT2 control the flow of the hydraulic oil in both the normal and the reverse directions between the hydraulic pump P and the hydraulic actuator C. A switching valve V controls the flow of the hydraulic oil in the normal and reverse directions between the hydraulic pump P and the hydraulic oil tank. [0007] The hydraulic driving unit OU also includes a slow return valve SV, which prevents hunting that might otherwise be generated when an external force is applied by the driven body W while the hydraulic pump P is operating. The slow return valve throttles the flow of hydraulic oil from a bottom-side oil chamber C2 at the bottom side of the hydraulic cylinder C to one of the check valves OT2. The other check valve OT1 connects to a rod-side oil chamber of the hydraulic cylinder. [0008] Relief valves RV are provided in lines that branch back to the hydraulic tank T from the main lines between the hydraulic pump P and each of the operate check valves OT1 and OT2. These relieve valves allow excess hydraulic oil to escape back to the tank T when an abnormal pressure is generated in the pipe line to which the relief valve connects. [0009] An additional line branches back to the tank OT from the lines between each of the operate check valves OT1 and OT2 and the hydraulic cylinder C. This additional line is provided with an emergency manual valve so that oil in the lines from the cylinder's rod-side oil chamber Cl and bottom-side oil chamber C2 can be released back to the tank when, due to a loss of power or some other problem, the pump cannot operate and is stopped. Opening the emergency manual valve MV thereby enables manual operation of the hydraulic cylinder C. [0010] Such a hydraulic driving unit thereby ensures safety, reliability, and the ability to avoid an accident or damage to the unit by preventing breakage in the unit even if an abnormal pressure state is encountered while the unit is in operation. [0011] A portion of the hydraulic pump P that relates particularly to the invention is described in more detail below. [0012] As FIG. 5(b) illustrates, the hydraulic pump P in the unit OU is mounted on the side of a housing body Hc, inside of which various hydraulic lines are located in addition to various valves OT1, OT2, and V, of the types described above. A lid-side housing Hb is fastened and fixed by a fastening bolt Hj over the pump. An oil-tight seal is formed between the lid-side housing Hb and the body-side housing Hc, so that the pump is contained inside the tank and oil cannot leak out of the tank. [0013] The hydraulic pump is located so that it is close to the source of hydraulic oil, which improves pumping efficiency. If hydraulic oil leaks between the body-side housing Hc and the lid-side housing Hb, the hydraulic oil leaks not to the outside of the unit OU, but merely into the hydraulic oil tank T, which confers on this unit a certain degree of safety against that particular potential failure. [0014] The body-side housing Hc and the lid-side housing Hb are combined to form a combined housing structure Ha. [0015] The means by which the body-side housing Hc and the lid-side housing Hb are fastened and fixed together is described in detail below in connection with FIGS. 5(c) and 5(d). [0016] The hydraulic pump P includes, in addition to the above-mentioned body-side housing Hc and lid-side housing Hb, a driving shaft Hd, which is driven by an electric motor (not shown). A driving gear He is fixed to the driving shaft Hd, with a driven gear Hg meshed with the driving gear He. The driven gear Hg is mounted on a rotary driven shaft Hf. A hydraulic oil port Hh allows hydraulic oil to flow in and out of the pump as these gears rotate. Mounting holes Hi are provided for mounting the lid-side housing Hb to the body-side housing Hc. [0017] In this configuration the hydraulic pump P is fastened to the body-side housing Hc and the lid-side housing Hb by the fastening bolt Hj. These elements are assembled in an oil-tight manner so that hydraulic oil cannot leak between them. If hydraulic pressure above a predetermined maximum allowed pressure is generated inside the hydraulic pump P or the lines connected to it, the hydraulic oil is allowed to escape through the relieve valve depicted in FIG. 5(a) back into the tank so as to prevent breakage of the hydraulic pump or other such damage. [0018] This construction, though, requires the relief valve and its related lines to be provided as separate elements, which is problematic in units such as this one in which simplicity and reductions in size and costs are very much desired. [0019] This is true not only in the particular hydraulic drive unit described just above, but in other various hydraulic driving units, hydraulic pump units, and hydraulic pumps used in similar conditions. [0020] The invention was developed in response to these concerns and in the context of an effort to provide a hydraulic pump in which damage due to unintended high pressure conditions can be prevented without the need to provide a separate relief valve. Pumps that embody the invention can be used in hydraulic pump units and in hydraulic driving units that include such a pump. SUMMARY OF THE INVENTION [0021] The invention provides a hydraulic pump that can be used in a hydraulic pump unit in which at least the hydraulic pump and a hydraulic oil tank are integrated together so that a housing of the hydraulic pump is contained inside the hydraulic oil tank. The housing of the pump includes a body-side and a lid-side housing that come together at a surface perpendicular to a rotary pump shaft of the hydraulic pump. The lid-side housing is brought into oil-tight contact with the body housing at a predetermined pressure that corresponds to a maximum allowable pump hydraulic pressure. [0022] The invention may be further embodied in a hydraulic pump unit or a hydraulic driving unit that includes such a hydraulic pump as one of its working elements. Continue reading... Full patent description for Hydraulic pump, hydraulic pump unit, and hydraulic driving unit Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Hydraulic pump, hydraulic pump unit, and hydraulic driving unit patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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