EFFORT REDUCING START MECHANISM FOR HYDRAULICALLY PROPELLED VEHICLES

Abstract

A propulsion unit 10, used to propel a line striper, is provided with a gasoline engine 12 which may have either a pull/recoil or an electrical starter. Engine 12 is connected via a centrifugal clutch 14 of a known type to a hydraulic pump 16 which includes a hydrostatic drive unit 18. In the preferred embodiment, the clutch 14 is designed to engage between the cranking speed and the idle speed.

Description

TECHNICAL FIELD

[0001] This application claims the benefit of U.S. application Ser. No. 61/015,057, filed Dec. 19, 2007, the contents of which are hereby incorporated by reference.

BACKGROUND ART

[0002] Line striper propulsion units are well known such as those sold under the LINEDRIVER trademark by the assignee of the instant invention. In such units, a gasoline engine directly drives a hydraulic pump that supplies a hydrostatic drive system. While such units work well for their intended use, when used in colder temperatures, the engine is hard to start because the high viscosity of the hydraulic fluid at lower temperatures makes it hard to (pull or electrically) start the engine.

DISCLOSURE OF THE INVENTION

[0003] A centrifugal clutch of a known type is placed between the engine and the hydraulic pump. In the broader sense of the invention, the clutch is designed to engage just above the engine's idle speed. In the preferred embodiment, the clutch is designed to engage between the cranking (recoil or electric) speed and the idle speed. In this preferred embodiment, once the engine catches, the clutch will be engaged to that there will be no engagement or disengagement during normal operation.

[0004] These and other objects and advantages of the invention will appear more fully from the following description made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.

BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 shows the engine-clutch-pump combination of the instant invention.

[0006] FIG. 2 shows a schematic layout of a propulsion unit.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] A propulsion unit, such as would be used to propel a line striper, is generally designated 10 and is provided with a gasoline engine 12 which may have either a pull/recoil or an electrical starter. Engine 12 is connected via a centrifugal clutch 14 of known type to a hydraulic pump 16 which includes a hydrostatic drive unit 18 which is in turn connected to wheel motors 20. In the preferred embodiment, the clutch 14 is designed to engage between the cranking (recoil or electric) speed and the idle speed. By way of example, the cranking speed may be 600 rpm, the engagement speed 830 rpm and the idle speed 1440 rpm. In this preferred embodiment, once the engine catches, the clutch will be engaged to that there will be no engagement or disengagement during normal operation.

[0008] It is contemplated that various changes and modifications may be made to the propulsion unit without departing from the spirit and scope of the invention as defined by the following claims.

Claims

1. In a propulsion unit having a gas engine, a hydraulic pump driven by said gas engine and a hydrostatic drive, the improvement comprising a centrifugal clutch being driven by said engine and driving said hydraulic pump.

2. The propulsion unit of claim 1 wherein said engine has an idle speed and centrifugal clutch engages above said idle speed.

3. The propulsion unit of claim 1 wherein said engine has an idle speed and a cranking speed and centrifugal clutch engages between said idle speed and said cranking speed.

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